Small claims cases are fairly easy to file. It would be interesting to see how to judge would react to all the bitcoin transaction explanations. I'd think someone who actually starts to go through the motions of filling a claim might get some help/support/donations from the community to see the case go through.
If you trade your new iPod touch for someone's BNIB PS3 that when you get home and open is stuffed with a brick, there's no reason you can't sue even though there was no exchange of money involved. In fact local scams for giftcards are quite common, and a trade of product for giftcard isn't that different than a trade of product for BTC.