Sitting on Yoga Ball?

I know all sorts of exercises to use with a yoga ball, but i've heard of people just sitting on it very often, instead of a chair while on a computer or watching t.v. etc.  i was just trying it out and didn't really understand the benefit.. 

 As far as calories burned, probably increases the burn from about 0.8cal/min for chair sitting to about 1.0-1.1cal/min - not much, but it has an effect over time. However, the main benefit would be in increased core strength and stability over time, by constantly balancing yourself - it helps your posture immensely, and improving posture to stand up straight instead of slouching improves appearance immensely. Just try standing up straight vs. hunching over and observe what happens to your stomach ;)

There are a few people in my office that sit on balance balls everyday. I think it does wonders for my posture, but I have noticed that some people sit on them with poor posture. The slouching on the ball and constantly rolling around definitely doesn't seem like it would do you any good.

I tend to stay in motion more when I use the ball as opposed to a chair. Plus more effort to stand and sit each time I get up. What I really like is when I'm on a boring call I can do modified situps or deeper side to side motions.  I just have to be careful not to go too far. I have lost balance completely a time or two. LOL