If you're going around corners "briskly", the wear is expected. I tend to wear out the outside shoulders of the tires on my "fun car" first...
If there's significant positive camber, you may also see that sort of wear. Particularly if it's in conjunction with a lot of toe angle. I'm not sure if it's toe-in or toe-out that does the job on the outer shoulder; I know that negative camber and toe-out will tear up the inner shoulder of the tire pretty quickly.
-soD