I think I'm probably the most qualified to talk about this. It's definately a problem that will never be resolved. Breasts and balls get in the way when doing Yoga asanas. I've crushed mine when doing this move before http://limbermen.com/Ritchie/Rc%20-%20b ... 0twist.jpg When I'm doing in a show it's difficult to stop.
I am not a yoga practitioner, but I've had similar problems with swimming trunks (when they are wet and stick to you). My solution was to wear a speedo underneath my shorts - problem solved. Now, a speedo and yoga may not mix so well, but you may want to try a pair of spandex/biker shorts underneath your yoga shorts.