I don't honestly think transit providers (other than comcast) are going to cause NN problems. They've been doing their thing for a while and have a clear model: the more bandwidth you use, the more you pay (either usage or connection size). Every once in a while, there's a peering dispute about weather Cogent qualifies as a peer. Someone who is connected to a transit provider can likely switch to other providers (or use multiple) much easier than a residential customer. There's also an array of providers that give you virtual presence at major peering points.