Sure, you could tell yourself that you'll use the time away from your computer to unplug from all the fascinating goings-on that the exciting world of social networking provides, but what if something anything! happens and you don't find out about it until hours afterward? You'll never forgive yourself!
If you're on Facebook and Twitter, using two apps to keep up with both networks can get a little tiresome. Seesmic hooks into several popular social-networking and blogging services to deliver you updates, all within the same app. You can post to multiple accounts in one fell swoop as well.
See also: Facebook, Twitter, TweetDeck, Foursquare