I'm rather careful about where I go when I'm at work. I only come onto TCS when there is a certain thread that I'm following closely. I don't even log in at work.
My company has been blocking the sites where there is a lot of band width required like you-tube, internet radio, winamp (because of internet radio). The only problem I have with it is that they put the the scary looking page to say the site is blocked on a MS Sharepoint site so when you try for a site it has banned, it wants you to log in to see it
Since I haven't had any interest in facebook or myspace, I don't know, but I'm thinking those sites are banned also. The only time I couldn't understand it was when it blocked the United flight arrival page.
The company pays for my computer, the network, and my time there so I believe that they can do whatever they want. I'm glad it is open enough for me to look for technical programming because I don't program well without it.