it's usually the older, washed-n-worn quite a bit, or the lighter weight shorts that get sheer. Stick with 6-8 oz shorts, they're much denser.

and I wear mine au naturale too, I don't use Chamois Creme and I've never had problems except with cheap shorts.

Right now I"m wearing Sugoi (which I just tried for the first time and LOVE), Performance Centurys and I've got some Terrys to try.