I don't think this is necessary for basketball. Having played quite a bit of pickup basketball in SF (and other cities), if you want to play basketball just go

I don't think this is necessary for basketball. Having played quite a bit of pickup basketball in SF (and other cities), if you want to play basketball just go to the court with a ball. If there is nobody there, you just shoot around until enough people are there for a game to start. However more often than not on a weekend or other prime times there are already people there and you just join a random group and get in line.