I had a similar experience on the buy/sell board.
Someone said he'd take my item after confirming shipping costs and such overseas. Another member offered to buy it, but I felt obliged to honor the deal with the first buyer as he had said "let's do it. What's the PayPal address", etc. The second buyer (who is located quite near to me) was leaving for a weekend trip and would send the money immediately, so as to receive the item by the time he returned home. He appreciated that I wanted to honor the first buyer's deal, so bought a similar item while on his trip.
Of course, then the original fellow stopped all communication, though after a day or two started posting comments on the camera boards again. I won't accept any offers from him to buy in the future. It would have been fine for him to say that he had reconsidered, etc. I had even offered by PM, after a day passed with no communication from him, that I had received a second request to buy it so could he kindly let me know if he still wanted it. He didn't bother to reply, though I know he received the multiple requests. I was concerned that he had fallen ill or something and didn't want to think badly, but was none-to-impressed when he simply started posting in discussions again.
This community is one of the finest on the Net in my opinion. I have sold some items on the buy/sell board to people who I consider to be great community members here. I look forward to interact with these same people and many more, and thankfully, there are few who show little respect for others. A few "sub-par" visitors is to be expected, but GetDPI overall has some very responsible and respectful participants.