We prefer mark's use of the email function... Not so fond of matching via social networks... unless it too works on the same function as mark's suggestion where the exposure is on the information submitting party.

Also email searching might get awkward for plural systems like us (most of us use the main system email for our personal journals -- that MIGHT get really confusing, though a couple of us use our own throw-away emails for our personal journals).

I also like a combination of yourlibrarian and cavlec's suggestion of interest matching and active communities.