I block anything naughty here at work. File downloads are a no go as well. Forums and BBS are still good to go though. Man, I can't see many places taking that away... if so... shoot, I think I'd quit.
We are pretty much the same on my end. We also filter content so if the forum has improper content it will also get blocked...
We run Squid as a cache proxy and Dansguardian as the filter all running on SUSE 10.1.