I just received an email advertisement from a "Web 2.0 security" vendor recommending that I use its product to block the evil Facebook. This is rather heavy handed.

Sales and marketing people want to use Facebook to reach prospects and interact with customers.
Sure there are issues with Facebook, but an all-or-nothing solution does not make sense. A more granular approach is much better. I discussed this issue recently in a post entitled, How to leverage Facebook and minimize risk.