500Gb a month? What do they do with all that data?
Although I do agree 140Gb is somewhat excessive, I think BT are all to blame for this, for forcing ISPs onto capacity based charging and user based charging. As the picture from a BT powerpoint presentation found on the UKIF site below shows, it costs the ISP a lot more unless they go for the "capped" option.
I get the impression BT want to screw every last penny out of us for what is obsolete technology. There is aleady (soon to be) uncapped Telewest 4Mb broadband available.