Remember how Comcast would never tell you how much bandwidth you used when they said you were using too much? A combination of insider informants and a company spokesperson has narrowed it down to somewhere between 90GB and 200GB per month. Apparently the limit depends on the market as areas with older and slower networks are subject to more stringent enforcement of the limit. According to the insider, Comcast also has a system to prompt you to buy a higher transfer limit when you get too close to the edge. Why haven't they deployed it? They want someone else to try it out and see what the backlash will be. (Hint: customers will be ticked.)
It's so nice to know that unlimited doesn't mean unlimited. Thank goodness most UTOPIA providers (like Xmission) clearly post their transfer limits before you sign up.