The key difference being body language. So much of successful human interaction comes from non verbal cues and if you're someone for whom that doesn't come naturally then socializing in WoW is not going to provide you the same benefit as in person interaction period.
If visual contact was essential for forming significant relationships then the blind would be unable to make friends.
http://www.flickr.com/photos/78553575@N00/321522242/
What can be learned by a blind person touching an avatar on a computer screen?
I think they do actually. Otherwise, why would people go through the trouble of meeting physically when they could do it on the Internet? It's not like people who meet in real life don't know about the Internet (I'm thinking of tech conferences, HN meetups, etc.) The physical experience is simply better.
Would orange flavored candy be a sufficient substitute here? I'd say no.
Maybe the blind are much less successful at making friends. What is your evidence to the contrary?