[Amadou]

Call me cheap, but I pay for my bandwidth and I don't want to have to deal with slow video streaming or high ping times just so someone I've never met can buy their drugs on silkroad.

A key thing to remember is that each person's social network is relatively small. You don't have to relay traffic for someone you've never met, just for the people you've added as "friends" plus some relatively small amount of overhead for linking into the rest of the "world" in order to do searches for people you want to add as "friends."