Should libraries have policies regarding social software tools?

Since having the responsibility for a few initiatives passed on to me for creation by a librarian, I have become quite interested in policies in general.  While I think it is a great idea to start new programs in a library, it is often the case that a flash of brilliance is not coordinated with a product's continual use. Therefore simply having a few rules in place at the start at of the initiative can help everyone aquaint themselves with what the constraints of the system are and allow for creativity to flourish within those constraints.  If in the future it becomes obvious that the rules are hampering creativity then the rules can be changed.  However it is always helpful to everyone to say "this is what is supposed to be done and that is what I am doing."  It relieves those in the chain of command from having to guess what their supervisor would do in a particular situation and then do it.  I do not think that it is necessary to write a rulebook for every situation, but it certainly can't hurt to examine possible points of contention during the early stages of an initiative and respond accordingly.