Anant’s written a post about Orkut Crush which makes fascinating reading. Maybe it’s been happening across many social networking sites, and I just haven’t seen it; possibly because I haven’t used the “looking for someone” facilities.
Orkut Crush allows person A to register aÂ “crush” on person B, and vice versa; the registered information is only provided to the matched pair when both sides signal.
So at a level of abstraction it allows a signalling of intention, done in secret, with the intention only revealed to the other party when matching conditions are met.
There are many things that need matching. There are many ways of indicating interest or signalling intention.