[allworknoplay]

You and the other responder to my comment both raise a point that is extremely important and near/dear to me. I talk constantly about the need to establish tech "utilities" that can offer pure commodity services without being compromised by things like a profit motive, need to grow, etc. Authentication is a perfect candidate for this.

However, even given such a pure, charitable utility, OAuth is still the best way to do this stuff, and that's really what I meant in my comment. Authing through a universal standard means you're not tied to ANY parties, and you can always offer the best of the bunch as an option. In fact, any such "utility" should enforce interoperability/standardization as a primary feature, lest it leave its users subject to economic/political volatility.

As for forcing customers to be on google/facebook/whatever, I see this as a sub-optimal practice insofar as it does NOT include such a pure utility, but not for any other reason. I don't have up to date data on the topic, but offering both Google and Facebook OAuth surely covers almost everyone, and even for the occasional user of neither it would still significantly reduce account proliferation and bad practices if everyone forced people to sign up for one of a few select accounts vs. the alternative of everyone rolling their own.