Agreed completely.
My ISP put in a 60 gig cap last year. I surf, download anime, work from home 4-5 days a week, listen to streaming music, watch videos on youtube, play X-Box live (includes downloading videos, demos and lots of RockBand/Guitar Hero DLCs), play World of Warcraft, am constantly uploading pictures to Flickr and my blog, do a lot of emails (receive 300-400 a day for work alone), download about a dozen weekly podcasts and do the occasional download. I also download updates for the multiple OSes that I'm running (Windows on 2 machines and Linux on another).
My wife surfs the net, does email, listens to streaming music and plays some online games.
And you know what? We average around 40 gigs a month. Some months its in the low 30s, some months its in the low 50s.
Once our kids are old enough to start using the internet I'm hoping that this cap will be a little higher, but even then an 80-100 gig cap would be acceptable.