[cweagans]

You mean I can't create another account on Facebook, Twitter, or LinkedIn? Weird. I was under the impression that it was easy.

Social network linking != nudity filter.

[jaredsohn]

You can require a minimum number of connections; this isn't perfect since there are ways to fake this out as well, but I don't think it can be done for without investing time or money. (Also, it means that if you don't have many friends/etc. that you cannot use the service.)