That's what I thought too. Not to mention oddly requiring a Facebook or Twitter log-in when so many people here complain about it (and all the stories about being hacked lately).
The main reason I choice it was because I only have to hold an integer id of your account id on twitter or facebook. If my database was ever compromised, there is only that piece of info about you that would disappear. It's basically leaving all the security problems (not to mention lost passwords, etc...) as a problem for Twitter and Facebook to deal with.
Do you need a log-in? Can't people use it without logging in? I would think you might want to go long-in free for a while and see how you do. Are you sure its not holding you back? What's your bounce rate? Do people show up and then disappear when they get to the log-in page?