I stumbled across this page just before and found it an interesting read. As they say in the article rims are so often overlooked but are such highly stressed (and important!) parts.

 

http://www.tirerack.com/wheels/tech/techpage.jsp?techid=110

Loved this bit:

 

"It is important to note that track use and/or participation in racing voids the manufacturers' warranties of all street wheels"