It may help to provide a little more context. The reason that FB Connect is used exclusively is to solve the pervert problem that has plagued videochat applications.
The FB account is used ONLY to track users, and on the landing page we make it very clear that we never reveal your identity to anyone and that we never post anything to your wall or your friends' walls.
We use the FB login so that if you are reported for misusing the site we can block you permanently. The thinking is that if we just allow you to create a new account or login with different accounts, then the pervs will be able to continue to access the site even if they are blocked on one account.
On the other hand, I'm getting the sense that this could be a big problem for legitimate users. Perhaps having multiple sign-in options would be OK, assuming that if you're a perv you'd be wary of signing in using your real account info, and that you'd really be going out of your way to be a jackass if you waited til one account was blocked before and then signed in using another account.
I'm surprised that the HN community seems more averse to using FB connect than I expect most normal users are. Either that or people that are critical of FB Connect are more apt to respond to this.
Lots of food for thought though. Ultimately, the question is whether offering multiple sign-in options dilutes the security feature of being able to permanently block those who misuse the site. While it does dilute this slightly, I'm starting to think that the trade-off might be worth it if only allowing a FB sign-in is so repulsive to so many...