Richard Ziade has posted a good article that looks at Why We Love Rounded Corners?. He has some great theories, but my favorite comes from the comments…
As children we discover sharp corners hurt, so we quickly learn to avoid them and develop a preference for smoother, rounder corners.
There might be something to that, but I’ll go one step further: the fact that rounded corners are actually harder to create, whether you are adding elements to a webpage or sculpting them out of stone in the real world makes them preferable on an a priori basis. At any rate, there will be interest for a long time in easier ways of making rounded corners in web design.
