[whakojacko]

Yes.

1) Its some extra work for what is likely a tiny portion of their target user demographic (note: this isn't the demographic that would use a normal signup if it was an option as supposed to facebook connect, just the ones that won't use it at all if it isn't)

2) They get nice benefits of forcing people to use facebook auth, eg friend lists within the app. Turntable knows all of my friends who use the service, and can show me rooms that they are using. If there was an alternate non-facebook signon that I had used instead, this wouldn't work out

3) The signup is probably more frictionless for users, many of whom are fickle and might not sign up if it seems like a lot of work. I say probably because I don't have experience with tracking conversion rates or anything here-this is just a guess