David,
I'm surprised - I've bought and sold many things on AGon and always had great communication with all. But playing devil's advocate, as a seller, sometimes you get 5-10 emails a day, and it takes time to respond to all of them if you are working or have other issues (then again, I believe you should not list an item if you are not willing to talk to people). I always do - at least a quick note to let them know someone else has already given an intent to buy, or something like that. The email from the buyer also is important - some potential buyers just send something like 'will you take X less than what it was listed for' or 'I am interested' and nothing else - as a seller it is nice to get a well written inquiry, much like you'd expect if you were talking in person. As a buyer, on only one occasion a seller gave me a terribly written response, and because of it I did not go any further with the transaction.
I think your experience is unusual - in my experience this forum is very professional and better suited to good transactions than most retailers (with the exception of good 'high-end salons'). We represent a very small precentage of the population, most of whom find the hobby odd. This forum and its users seem to 'stick together' in my experience.