My original music band has been using it as a personal central communication point with good results. It keeps everyone up to date with where we are up to in developing our songs. This includes making a single post to let members who didnt participate in a session know that recordings of that session are up on our ftp server, practice times, recording times, who is required and when, if ppl cant attend. Even to let ppl know that a musical idea is there for ppl to listen to and give feedback.
We have found it has saved us a lot of time. Obviously there are many ways of doing the same thing but this has evolved naturally and is working well.
We needed a guitard solo from our old guit4rist who now lives in Atlanta so that we could finish off a song (spontaneous sound check jam if the truth be told) that we had recorded with him. We used FB for all the communication and the ftp server to exchange files. Everyone was kept in the loop and we knew when we could skype him or chat with him because we could see when he was online.
Worked realy well. It also alows us to keep in much closer contact with him than would otherwise be the case generally even after the fact.
Two of the guys in this band had similar attitudes towards FB as the more negative comments in this thread but now dont even think about it in terms of school kids flaming each other and posting that the sandwich they are eating has pickle or not.
Things are what you make them I guess.