Doesn't this just apply to retailers? If you're a social-networking start up wouldn't you really want users to create accounts rather than using their FB or Twitter accounts? Also, only something like 13% of internet users use Twitter so I wonder how useful it is. I only use my twitter account because I don't trust FB privacy settings.<p>I'm in stealth mode with my start up, but should I allow social sign-in once we launch is a question I have pondered for a while now. My gut instinct says to do it because it will make it easier for users to "get a taste" and then they'd want to create an account if they liked the service. But the more business minded/practical part of me says this would only defeat the purpose of a social network--why would you use one SN login to use another SN. Twitter (to my knowledge) never allowed people to use their fb login.