You can ask your participants to register via multiple methods - email, LinkedIn, Facebook or Twitter. Just get them to join in with their favorite channel and capture their email address
In my experience the conversion rate by letting people enter their email address is higher than a FB connect. Right now we're focusing on features that will get more results first - before adding "nice to have" features. So I'll push this one back for now - but we'll probably implement it at some point down the line. Thanks!