Curious, how many people do you need on a social network before you can find someone to talk to or before it is engaging enough for you?

I certainly don't need a billion users. I think I'd be happy with 100,000 users -- what is your number?

I think this is related to the question of how big of a city do you need to live in before you can find something to do and are not bored living there. I'm fine with a city of, say, 50,000-100,000. That is more than sufficient for me to find an appropriate number of likeminded friends and neighbors as well as interesting pursuits.