@Bill - We allow LinkedIn, GovLoop, and Twitter, and probably a few more I can't name off the top of my head. Facebook is banned because some of their games exchange code with the browser and it was just this type of thing that hit us last year. Folks are putting up game and polling modules there all the time and I don't have the confidence in Facebook's testing than I would have in our own.
I understand about social networks being beneficial, but with Facebook, I can't see how playing Farmville all day is going to help productivity (grin).
The socialware software is interesting, but I can hear the budget argument now. It will likely be a while before management sees the value of some of these sites, but I do hear you. Thanks!