Just after I posted, I realised that the content on the site is entirely populated by your Facebook/Twitter connection, so I withdraw my righteous indignation ;

Just after I posted, I realised that the content on the site is entirely populated by your Facebook/Twitter connection, so I withdraw my righteous indignation ;-) A promo video would help showing potential users where the value is. Or how about adding some public data for an example user? E.g. when an anonymous user views the homepage, they see the content for this example user. Then the Call To Action could be 'see your personalised content by connecting with FB/Twitter'. This would let new users get some value out of the site (or at least see how it could be valuable) before signing up.