TIA,
Sorry for the delayed response. We actually did a bit of research on this. Facebook used to have a policy against using the Like button to gate content. However, they seemed to have revised them slightly recently in a way that would make what you're asking for possible.
We'll have to do a little more research, but we've added this to our feature tracker of things to possibly add in the future. Our main concern is always making sure that we adhere to Facebook's policies. There are a lot of things that are *possible*, but many can violate what you're allowed to do.. and we always want to protect our users.
Thanks for feedback, and we'll keep you posted on what we find... or feel free to post a message in a few weeks to get a status update.
Alex