To try and boost Facebook followers, I've written a competition app:

But, despite advertising it to our 3,400 current followers (of which Facebook told me 1,400 were 'reached'), and also advertising it to my 100 or so real life friends and family, only 48 people have entered, anyone got an ideas why the competition is flopping so badly?
I'd thought it the prize was decent enough, and I think that the app is fairly robust (the only issue being if people have 3rd party cookies off, but I thought I'd programmed around that reasonably).

Any suggestions?