Folks are comparing the hidden data limits that Verizon uses to the hidden data limits that most of the hardwired landline providers have. Comcast has used them for years.
Verizon is now working to get rid of their "unlimited" users, and this is their method. Their CEO was just out saying that they can't make any money while they have "unlimited" data plans out there. Of course, other carriers ARE, and he is retiring in a few months, so we may see an about-face from Verizon then.
Verizon is also cracking down on folks that were using the T1114 routers with "unlimited" plan SIM cards. They are sending letters to them that they need to use a supported device or get cancelled.
As for what constitutes excessive data - that's why all of these limits are hidden/flexible. The carrier can say it's whatever they want it to be. In this case, it looks like Verizon is using 100BG as their number for the moment.
As a full-time homeschool/roadschool family with no satellite or cable TV, our usage ran from 300GB to 400GB a month using Comcast cable internet while stationary. That includes everything - e-mail, web surfing/research, me working from home from time-to-time, and streaming video. They never said anything about it. Same with Cox in Las Vegas where the usage was the same.
Right now, we have a plan with T-Mobile (prior to T-Mobile ONE) that gives us unlimited data on the phones (2) and 7GB per phone of tethering. We also have a Z-917 hotspot that gives us 22GB of high-speed data and unlimited reduced speed after that. We plug the Z-917 into our Asus RT-AC66U router and all devices can use it, likewise we can plug the android phones into it and use the 7GB per phone as well.
We have found that using apps on the phone for Netflix, PLEX, and other video applications and the Smart View streaming feature on the phone to a Roku connected to the TV with screen mirroring turned on, we can get "good-enough" quality. That leaves the Z-917 and the phones for everything else.
Unlimitedville is back - to a point - and has a 150/month unlimited T-Mobile plan and a 250/month unlimited Verizon plan. I've been trying to get more details from them. They indicate that folks often exceed 300GB with no issue, but we haven't had a chance to test that.