On another note, if someone offers to run you through an instance, follow their instructions. Seriously. If they tell you to wait somewhere, wait there. If they tell you to follow, follow. If they tell you not to touch things, do not touch things. This goes doubly if the person running you through is a healer. They may not have the dps to burn things down in a second like a rogue or a hunter would. They are there out of the kindness of their heart so you don鈥檛 have to wait in LFG; respect that and be courteous.
In short, right now, this isn't a problem. While in the future, Comcast may try to bring the Guild Wars Gold bandwidth cap lower and lower, at this point, it doesn't effect enough people out there to worry, and even if you are affected, there are likely steps you can take to get around it, including going with another ISP if that's an option.
And if you do get suspended out of the blue? Best option is to just use another ISP - even if Comcast isn't willing to support people who use tons of bandwidth, there will likely be another company that does. And if high-level broadband does become really widespread, it would be a bad business decision for Comcast as well to suspend large numbers of their userbase - while there's always the WoW Power leveling chance that they could start charging a premium for more bandwidth, smaller companies will likely step up to fill any spaces that Comcast tries to screw over.