Facebook err, at work...
I think that someone in Redmond accidentally drank hydraulic fluid at the last company beer bash, TBH.
Seriously - I would rather masturbate with a cheese grater than try and emulate Facebook activities in a work environment (I'm the one who has to support all that shit at the back-end, and I find SharePoint to be an over-priced resource hogging headache, so maybe I'm biased here).
The only employees I can see offhand who would even want that would be the ass-kissers, the employees more interested in doing politics than work, that one creepy exec who really doesn't do much during the day beyond surfing dodgy sites in his office, and the terminally brain-dead.
Besides, if the proxy logs are accurate, employees with web access are too busy surfing the real Facebook all day long (yes, I'd love to block it. No, I don't want to have to deal with managerial fallout if I did do it. Best I'm able to do w/o getting lynched is to block anything coming out of Zynga and its ilk).