Are you planning more login API support other than just Facebook? I'd imagine you want to run the gamut: twitter, foursquare, etc - maybe even get rid of your own login altogether to make it easier for people (of course this limits you somewhat - but I'm pretty sure your target audience has at least one of these accounts)
Yes, we are thinking about it, though people may be afraid of linking it to their social accounts, therefore we will continue to support our own login system.
Please never suggest this to anyone ever again. I'm so sick of having to authorize apps with vague descriptions of what they'll have access to.
You're making the generalization that this app will also do it wrong, and maybe that's likely, but I think it's too pessimistic.
If every single application everywhere rolls it's own auth every time, you're going to have 10 auths (which according to security advice should be seperate) to remember.
regardless of implementation the idea of unifying (or even semi-combining) login is not a bad/not worthwhile idea
You're confusing with what is [perhaps] technically the most reasonable solution with what your potential users will be willing to do. That's a mistake.
Can you elaborate? Are you saying that the most reasonable technical solution is what people should select, regardless of what the potential users are willing to do?