I have never gotten into this Walmart parking battle before, but I feel the need to put in my 2 cents worth. Why should RVer's feel that Walmart or any other private business should have to open up their parking lot for free camping or be considered unfriendly? I realize that many who use the parking lot for overnight "parking" purchase items in the store, but my guess is most would purchase from them anyway. I have never spent the night on a parking lot (Walmart or otherwise) and would never do so unless forced to by circumstances.
If someone is only stopping for 4-6 hours off the road, I don't want to be around them on the road. Even truckers have to stop for more that that. We have always stayed in a campground and try to be off the road for a least 12 hours, so we are well rested for the next day.