I'll try to come up with some cons as I ramble on. Remember, you asked for all this. :) I had many of the same concerns as you and with only 3 years experience I'm still learning. As Donno128 said it can mean different things to different people. I cant imagine you ever getting shot as you dont just roll up and park anywhere you like. You will mainly use the resources available that guide you to where others have already been. You can explore and find new places and add them to the websites that list boondocking places.
Places like BLM will often have signs pertaining to open or closed areas and time limits. 14 days is common and I would NEVER cheat. Some BLM areas will also have sections of LTVA long term visitor area. I believe it's about $180 for a season pass with some areas having no services and some having dump station, trash water on site. Same areas are sometimes $40.00 for 2 weeks which still isn't bad if the area is closer to town or whatever else you need.
Each state may be different in how it all works. If you look at freecampsites.net for Michigan you will see that it mainly shows a few casinos yet there are hundreds of thousands of acres to camp on. The DNR website explains dispersed camping and has a permit that can be printed. You are basically allowed to camp anywhere on state land as long as you go by their guidelines. Although the issue is accessibility. You will find many dirt roads or what we call fire trails through the woods but you dont know which ones you can venture down and be able to turn around in. In places like that I have used my bicycle to scout the area before pulling in. Same thing in some of the Florida remote areas. The road or trail looks fine but you dont know what happens a 1/2 mile in where the campsite is supposed to be.
Out in the desert areas it's much easier because it's so open. You can see other rigs and easily figure out how they got into their spots. It's also nice because there are often no trees to worry about and so much room to turn around. It surprised me that so much of the desert surface is so hard packed. Some areas are rather course stone on the surface yet others are finer texture. I have ridden my bicycle for miles with the only real obstacles being washes.
I basically try to camp for free while realizing that's not going to happen 100% of the time. There are times when I have stayed at rv parks to dump, fill, laundry etc. There are numerous sources for boondocking such as Dept of Agriculture, National forests, BLM, COE, county and city parks etc. One of the main resources that I have had great luck with is freecampsites.net. Before I leave I try to plan out a course with that website and try to have a couple backup plans. If I get to an area that I dont like because it just doesn't feel right or it's tacky looking or the space is too tight or whatever I can leave and have some idea of where else to go. The backup plan may even be a Walmart or truck stop but having multiple choices let's me operate without having a crisis on my hands when it's getting dark out. It's bad when something doesn't pan out and it's late and even a Walmart is 60 miles away. I think I have been to one or two from that site in three years that had bad directions or I couldn't find them but I have also found many fantastic places.
I also use google maps with street view and earth to try to check an area out. It often times wont let me see exactly the area I want to camp but it gives me an idea what the area is like. I can look at gas stations to see how easy they are to get into etc.
We can basically stay out for two weeks and then have to dump the black tank. I do have 15 gallon blue tote. It's about as big of a tank as I can slide up a 2x10 board to get it up in my truck bed. It can be emptied from free to about $10.00 usually with a wide range of places to take it. I never dump black on the ground and dont urinate outside. If we stay at places that have outhouses I will sometimes use it so we can stay out longer. Sometimes even somewhat remote camps may have water but I have bought it at Wmart and gotten it free at gas stations and rest areas. When we were near Yuma they had water stations everywhere for .75 to $1.00 for 5 gallons. I carry four 5 gallon jugs and our rv holds 60. Some places allow gray water to be dispersed on the ground, depends on the area. Certainly not in more populated and crowded areas. It's more of a remote area thing.
The other big issue is coming up with your energy management plan. Generator, updated converter, updated wiring to get the converters power to the battery, solar, inverting, house furnace vs cat heating etc. It's not difficult but can seem overwhelming at first. If you end up being forced to a park every few days to charge it gets pricey.
As far as leaving the rig, it all depends on what the area is like. I prefer to have others in the area but not right next to each other. I recently met someone online who was coming to our area and wanted to be near someone they knew when they left their rig to go to Mexico for the day. They knew the general area but were unsure about being out there so they started asking online. The area was actually very safe and many of the people parked there came every year and knew each other. As the new guy I was surprised when meeting people that they often knew who many of the other people are. I believe some people are scared to death to be anywhere but a commercial campground so they will pull up and park 15 feet away when the area is 100 acres.
I have never had any theft problems but I keep things pretty tight. Don't leave the gps on the dashboard or expensive lawn chairs out, Put the generator away all the time when you are done with it and don't depend on a cable. Don't leave the generator in plain view all the time. At some places I will lock the bicycles on the carrier every night, some places they sit out all the time. Some places that you camp are out of the mix of things and some have locals moving through or past the area. The guy camped near you is unlikely to steal your generator and more likely it would be the local boys. When you go to a crowded areas like Quartzite you have more riff raff and there have been posts about generators stolen.
You can do well by getting to know people and learn from them. They know where the dump and water are and good restaurants and stores. Many of them have been going to the same areas year after year. This will vary with the areas that you travel in. Just like rv parks, there are sort of pass through boondocking places and there are destination type BD places. Some places are seasonal and fill up with locals in the summer yet are empty during the winter. Some stuff in the South west empties out in the summer and even close.
I cant imagine where you will have wild animals attacking you. I'm from Michigan where the most dangerous animal would be a black bear. The only place I have seen one closely was at a landfill in the upper peninsula 50 years ago. They are around but it's not like they are out to eat you. If you stumbled on one when it has cubs with it that would be the most dangerous time. I'm sure places like Alaska are different and more caution is needed.
We have seen coyote and they wont attack you but I'm sure they would go after a dog. I have heard they will get a dog to chase them and then a group will kill the dog. I dont have experience in the worst bear areas but my understanding is that in general you need to make noise. They generally are not out to hunt you and most encounters center around startling them or running into them with cubs. Raccoon and possum will get into coolers but wont attack you. I have seen a porcupine chew through the floor of an long unattended TT and tear all the cupboards up and chewed on everything in there.
I guess only real negative would be dealing with the dump and water. On the other hand every time I go to the dump station or water I end up meeting and talking to others that share their camping spots and other resources.
It's always interesting to talk to people who are all doing the same basic thing yet all doing it in vastly different ways. One guy is using 800 watts of solar and the next guy gets by on 20 watts. One person drives 50 miles a day and one drives 400.
Often times when people are new to this they will do a lot of moving around and slow down as they find the places that they like to stay. We dont like moving a lot, yet we dont want to be right next to anyone so boondocking works well for us. As we travel we also find out where we might end up parking longer term and possibly even move to.
Since leaving home on September 5 my per night cost is about $1.60. That doesn't include water or dump fees.