I'd have to agree with the seller on this one (but I've been in the buyers situation in the past). The lesson here (I think it's been mentioned but I'll repeat it anyway), is PROVE your commitment (make a deposit). I saw in the thread, the seller mentioned that he had someone coming to see it on the same day he intended to make a video. A little "good faith money" would clearly show your are a serious buyer.
Some of these games, much like the other product I peddle (Real Estate) can be hard to move when it's time, so you have to take the guaranteed sale when you have it. I'm not going to pass up a cash and carry deal, for a conditional offer, without getting some assurance. Just like I wouldn't fault the buyer if they flaked...err..changed their mind (I'd just say a few bad things about them under my breath), you can't fault the seller for taking the "bird in hand". I'm a collector, not a vendor. So I'm not in this for profit. There are a few people I've worked with on KLOV that I'd extend additional courtesies, having worked with them in the past, but the majority of KLOVers are total strangers, so I have NO expectations, good or bad, until I get to know you.
So to the buyer, I feel for you since this deal went sour, and if in your opinion, you won't want to work with the seller in the future, that's understandable. But I don't see it as a breach of KLOV "etiquette" to let the game go to another buyer. In my opinion, I'd rather not see "negative feedback" used as a tool to express one's disappointment. I'd rather see it used to alert the community to those very few people that do try to take advantage (e.g. taking payment and not delivering, selling "broken" as "untested", etc.). KLOV should be no different than any other place you interact...you are going to like some people and not like others. It is a COMMUNITY, not just a marketplace.