Well, as more and more movies/tv viewing and all that start streaming through the internet, the average person is more likely to start hitting that cap. Not just the IT/engineer kind of person who uses massive amounts for data transfers.
An average netflix movie is 1-2gb, and the average tv show is 300-400mb. Well we got the basic DVD quality down, now people want more HD movies and shows (like through Hulu and Vudu). So now it's up to 8gb movies. Play those 2-3 times a week and that's 24gb x 4 weeks, averaging just under a 100gb a month on just movies. Got more than one streaming device, kids in one room, parents in another, it'll be quite easy to use even more than that.
The gaming industry is moving more and more towards downloadable games. It's cheaper than having to produce discs, manuals, cases, and then paying the middle man (retail stores) to carry the games. It used to be just small 1-2gb games, that were simple like Tetris or Angry Birds, the cost was usually around $10-15. Now it's full games that are 10-20gb, the cost is usually around $40-60.
Patches, updates, and the wonderful DLC (download content, just to squeeze a few more bucks out of a player), are all through the internet. There's some games that wind up with 2-3gb updates (like Unreal Tournament).
Then there's the great online community so players can play against each other from around the world. Well there's more internet streaming. It's very little in comparison, but it does add up over time. Especially for the WOW users who are addicted.
Now that we've got our media covered which is probably going to be the greatest user of internet bandwidth, there's the basic internet browsing. Most sites are under a 1gb, but there's more and more sites popping up that are larger than 1gb.
People are always wanting better quality, and companies are finding it easier and easier to provide the better quality, but the internet companies don't want to keep up with the new technology that's available. Remember the olden days when having DSL was a big thing and expensive as heck? In 2004 I was paying $50 a month for Bellsouth DSL (around 1mb-3mb per second), now $50 a month can get you 6mb-18mb per second. As long as people have the speed to download, open files, and view large web pages, they don't seem to notice how much bandwidth they're actually using.
As we move into a world of everything is on "my time", people are going to want to do things when they want to, not when some one else says so. People don't want cable, because A) it's too expensive, and B) they don't always have the time when it's actually on to watch their shows. Look how many people "wouldn't survive" without their DVR boxes. The internet and streaming allows for people to do things on "their time".
