Difference between bitcoin and testnet, really Other than what is listed in the wiki, what is the difference between the two networks?  

Could you sell test Bitcoins for money if you could find someone willing to buy? 

What would happen if you tried to send test Bitcoins to a 'real' account and vice versa?
Testnet bitcoins are less widely used in commerce than mainnet, and are not perceived as intended to be a currency.
Yes, you're unlikely to fetch a significant price though.
The transaction will not be recognized as a valid transaction. It would essentially be an irrelevant jumble. In fact the client wouldn't allow you to send anything because the address won't match the format of the respective network.