This would be similar to going short on BTC. If the price decreases, you will profit.
That is a pretty short expiration but even so, you aren't giving much of a forward premium to the seller.
If you can't find a trade here, you could also try offering it as a call option.
;;buy 77 btc at 6.75 DWUSD "call option premium 0.01 BTC expires 10Jul2012"
Which would be if you found someone that wanted to trade with yuu, you would pay 0.77 BTC (77 contracts X 0.01 BTC) today, and then you have the option of paying $519.75 any time on or before July 10, 2012 to get delivery of the 77 BTC.
I've not seen much of this option activity on -otc ... but now that we have BTCrow and ThruCoin (?) escrow methods (when necessary, and Web of Trust making escrow not always needed), options could be something to try.