I won't use any service that require FB Connect.
I am already subject to lockin purely because of the social networking aspect - all my friends use it. Why would I want to lock myself in further voluntarily?
And before anyone points out that google is also a massive sinister advertising company, they have shown their commitment to data portability in a way that I presently find satisfactory. FB go to lengths to prevent data portability.
I myself was surprised when I found it.
I can't imagine what service that require FB Connect are thinking...
This allows us to give a vastly better experience to our userbase, while losing effectively nothing -- our demo is non-techy 21-35 singles, meaning 95%+ Facebook users.
Edit: To clarify, I mean that no less than 95% of our demographic is already using Facebook.
It's possible. I would guess that people would be willing to take this "deal" if they believed that they'd be guaranteed that others also have to take your deal. However, aside from a person's desire to present themselves as they choose rather than as you choose, the problem might that some would create Facebook accounts only for dating and thus control their presentation better than the average person who wouldn't bother. But perhaps your users wouldn't consider such deviousness (and don't tell me you'd filter those people out - the account themselves could perfectly real, just accounts only created for a purpose).
Personally, I wouldn't accept this since I want to control how I'm represented. I don't fully trust Facebook but I might trust them with something things. I don't trust you but I might trust you with some other things. Giving you and those like-you my FB information means that I'd have to suddenly start putting unlimited in both FB and you. Maybe some people are OK with unlimited trust and "openness". I doubt there will be increase in such people over time - I could be wrong.