Right. It turns out a lot of the work comes from gluing the various services together. For ex, when a user signs up with an email account, and then forgets and signs in with Facebook next time.

This takes care of deduping accounts, and flattening the social data, etc.

(FYI, I'm with DailyCred)

Looks really cool. We took a swipe at this at Bagcheck as well through search: https://bagcheck.com/blog/02-design-solutions-for-new-log-in...

In that case, amazing. I've been looking for something like this. Will have to give it a try.