I did meet a friend of a friend one time and Second Life came up in our conversation, he gave me his avatar name and I did my best to avoid giving him mine, I was glad when the subject changed as he was way too into me and I didn't want him bugging me in
SL as well.
Aside from that, it is just random friends I already knew before
SL anyway. My first life partner also sometimes logs onto my alt, who I am partnered with in Second Life, though I don't think that really counts.