I don't know what things are like at your company, but here at the Fun Factory we use an internet blocking program to prevent the worker bees from surfing specific web sites. Over the years, the noose has been tightened around which sites are "work appropriate" or not.
Some of the sites that are blocked include sports, internet mail (ie, yahoo, gmail, hotmail, etc.)shopping, chat, blogs, and social networking. I think we all understand this at the conceptual level. It's not appropriate to have folks "stealing" from the company by using time to surf the web for non-work related information. But it is frustrating when you want to take a few minutes to check a score, news headlines, or what's going on in the markets.
Of course, most folks have come up with a workaround. Some have brought in their own laptops with wireless cards. Others use smartphones. In addition, RSS (site syndication) allow folks to keep up on their favorite sites in an RSS reader (Bloglines, Google Reader, etc.) without tripping the blocking software triggers.
I think while the companies may be successful at preventing the worker bees from using company resources to waste time, the biggest resource being wasted may be labor. The cost of labor is the biggest expense for most companies, and having workers go to extremes to take their mental breaks from the 8-to-5 grind may be counter productive.
Just thinking out loud on this one. And tired of texting blog entries from my cellphone...