Geez, I wonder if I have a cap too. I just always ass/u/me-d it was unlimited. I do have one of those fancy-pants "Triple Play" deals for TV, phone, and internet. All the movie channels, Quantum speed boost, etc. It would be just like Verizon to give you extra speed so you burn through your data faster.
Here's my Comcast data usage meter info for September, Oct. and Nov. The average use by Comcast customers is 17gb per month. I'm on my phone constantly and my wife uses hers. I don't see how some use 100+ gb in a month. Movies?