Check out Force9 ADSL service. They have a premier and lite user package for thier home users. I feel most ISPs will use the same format. The premier user will pay for example £29.99 for 1mbit connection, unlimited download. The lite user will pay £14.99 for the same connection with a 1 gig per month download limit, but you can increase it up to 10 gig, but the price goes up with each gig.
I feel it's inevitable and soon all ISPs will be placing a download cap of some sort
