I think facebook will be a tipping point for the service right now 80% is done through reddit and 15% through twitter. If people can send microtransactions through facebook I think the service will explode.
+1
I am not so sure about this. Facebook is very insecure and accounts get hacked all the time. There would be too many instances of people loosing their money because their account got hacked
It would have to be implemented intelligently, but there are solutions for everything. And it would still be an amazing promotion even if the occasional account got hacked. There's always idiots who use "1234" as their password. Let them get robbed.