So you want to guage how many bitcoin users there are by how many people join your facebook group? Looks like a cheap way to try get likes in my opinion.
It's a FB group, you join a group, not like my profile
I don't think that it were be some results with this initiative. There are hundred of peoples that don't like Facebook and don't have a profile there. Then, there are other hundred that haven't read this thread and so cannot join because have no knowledge about it. And maybe there must be another third group that are lazy people and don't bother to go to register to this group. I bet that the number of this group will not be more than 300. When the users of bitcoin are at least 1 million (I guess). Let's see how will go !!!