Conduct on Audiogon

I am relatively new to Audiogon and have a question about how business is conducted on this site. This morning I made an offer to purchase an interconnect at a certain price and if the seller responded within the day. I received an e-mail from the seller indicating "I'll accept your offer" and notifying me that he would accept paypal or a money order as payment. At this point I have made an offer, he has accepted, and I am thinking we have a deal. 42 minutes later he sends me an e-mail saying he needs me to reconfirm within 10 minutes or he is going to sell to someone else. Of course I am not monitoring e-mail on a minute by minute basis since I have to keep my day job in order to support this expensive habit, and the guy turns around and sells this thing to someone else. In the regular, non-internet, world where I operate this type of conduct would be total b.s. But when I ask this guy how he can agree than simply back out he tells me this happens all the time on Audiogon. Is this really the case? Does this type of conduct merit negative feedback or am I overreacting?