Blocking it at the Firewall?

While thinking about Dconstruct type things I may as well throw the odd thought that comes along especially if related to a thought that originated at the conference.

I sent a message to two co-workers today, a valid work message. Someone else was using Facebook at lunchtime (more people seem to every day). A comment was made, at some point they will block this at the Firewall. Where I work things get blocked at the Firewall.

Thinking back to Tom Coates and his web of data, then soon (perhaps now) blocking at the Firewall will be pointless, the web of data remember.

Block Facebook, I can still read my Facebook notes via RSS in Google Reader, can still get a summary via the widget in Netvibes. I have only just started using it there must be many more ways.

How would you go about blocking Twitter?

Block everything and block communication fullstop?

Edit: Somebody at work (thanks :)) kindly pointed out this Guardian article.