I'm a pretty serious gamer myself. I play anything up to 4-5 hours a day, on bandwidth-consuming games like Team Fortress 2 and Gears of War 2. On top of that, I've got the same Windows updates as everyone else, and I'll typically use up 50-100MB browsing daily. Including patches and whatnot, I very seldom manage to consume my allocated 5GB of bandwidth.
Well that differs because I have a Mac and Windows machines.
My Windows machine(s) run AV, Spybot, Office and other apps (all need updates, AV takes 2-4MB daily by itself, sometimes more)
Windows updates
My Mac runs a Final Cut Pro setup which itself has frequent updates, plugins from numerous vendors which do updates - each update can be 60-100MB (for plugins)
Mac also runs OSX updates
Other Mac apps also like to update themselves
I also purchase videos online - mostly tutorials (subscription based)
Stock photography?
Online backup?
Your own website uploads?
Stock music? All those are done sometimes. Some are free, some need a credit card number.
Cheap bandwith is a necessity. Just because you're COOL with 5GB doesn't mean everyone else is a pirate. Its possible to purchase entertainment online too (downloadable videos), Games from sites like Gog.com and music.
Then there's tons of free stuff (not warez). Some sites release video for free
- and no-not everyone of those sites is in English. Music streaming sites?
Like to watch foreign TV? Like to listen to foreign radio stations for news and commentary? Like to download podcasts which are 3-5MB each?
Then game demos and program demos - PS demos are like 300-400MB each.
HTML browsing - sites now include inline video and graphics and ads play vidoes and banners - all that consumers b/w
I will say that 10GB is a minimum.