Maybe ethics do come into play, but I stick with my earlier statement of there being no duty to disclose, it's why we have the phrase caveat emptor.

Furthermore, you may say that hatred of non-revs has nothing to do with it, but when I read posts like:

http://www.flyertalk.com/forum/22896743-post59.html

And various other threads that quickly get locked where a non-rev is a bogeyman, it's hard to believe.