Anecdotally, the problem isn't that sites (e.g. Quora) don't trust FB Connect, it's that users don't. For every project I've worked on that had both FB Connect

Anecdotally, the problem isn't that sites (e.g. Quora) don't trust FB Connect, it's that users don't. For every project I've worked on that had both FB Connect and in-house login, almost no users used FB Connect, no matter how the two options were visually presented. I've seen iOS apps get absolutely HAMMERED in their App Store reviews simply because they don't have any login other than FB and users refuse to use it. I agree this is a problem, but if I'm a line-level engineer or product guy, my short-term goal isn't to come up with a high-level solution, it's to do what works and won't fuck with my acquisition funnel. Which is currently roll your own.