Nobody appreciates a blurry image. There are exceptions, of course, but in general most people want their images to be as sharp as possible with lots of fine detail.
One of the main reasons images can turn out blurred is camera shake, which in turn is often caused by shooting at too slow a shutter speed, especially when using a telephoto lens. And while upping the ISO can sometimes help, it can also result in a loss of detail along with an increase in undesired image noise. This is where image stabilisation technology can help.
All manufacturers have adopted the principle of image stabilisation and incorporated it into their DSLR systems, either in-camera or via special lenses.
Sony, Olympus and Pentax follow the former option, with image stabilisation technology built directly into their cameras (an exception being the Olympus E-450), while Nikon and Canon place it in specific lenses instead.
While there is no real difference between camera-based and lens-based image stabilisation systems in terms of the final image, stabilised lenses do of course cost more.