According to doctors interviewed by the New York Times, the way many people "cheat" at Wii games could be a threat to their health:

A common problem is the realization by players that a full swing is not required; a flick of the wrist is often enough to return a serve or bowl a strike. As several doctors pointed out, that is the exact motion — concentrating the force of a swing in the muscles of the forearm — that can cause tennis elbow.

Check out the full story at the New York Times's website.