As a real data point, the founder of Quora estimated losing 25% of his sign ups when it was a facebook connect only service[1]. [1] http://www.quora.com/How-mu

As a real data point, the founder of Quora estimated losing 25% of his sign ups when it was a facebook connect only service[1]. [1] http://www.quora.com/How-much-is-Facebook-Connect-limiting-Quoras-growth http://www.quora.com/How-much-is-Facebook-Connect-limiting-Q...