There have been tons of news stories about companies blocking (partially or even fully) internet access so as to "keep people working". I've thought that was a really stupid idea for a long time; would you want to work at the sort of outfit that treated you like a 5 year old in need of a filter? Here's more on the subject, from an MS employee with the title "Senior Design Anthropologist" (I love that title, btw):

Jobseekers will think twice about employers who lock down work internet access, a senior Microsoft executive said today.

“These kids are saying: forget it! I don’t want to work with you. I don’t want to work at a place where I can’t be freely online during the day,” said Anne Kirah, Microsoft Senior Design Anthropologist.

“People that I meet are saying this to me every day, all over the world.”

The web, IM, and IRC are all crucial parts of my job; I couldn't work without them. Manager who implement lockdowns (outside the national security zone) are looking at this completely wrong: if you have an employee who spends too much time browsing the web (etc) instead of working, then you could try actually managing - discipline (or terminate) the bad actor.

What we have in outfits that just "punish the class" are managers afraid to do their jobs.