Vent, I believe you will have trouble trying to convince people of changing their approach as you have experienced this even from a completely different angle to somebody who is there to sell material.
That is not to say that your response is not a valid one, however a discussion like this one which is based purely on individual experience will probably not end in a viewpoint that will please everybody.
From your perspective the folk who made up Artists Alley were not pulling their weight public relations-wise (please correct me if I have misunderstood), however as I mentioned above, the attitudes that have been projected from behind the table are based on the experience of those people. Many of which have mentioned that they have found - through their own experience - that most people do not want to be bothered and would rather browse at their own leisure. Your own opinion is that there should have been more of an effort to approach potential buyers (even with a simple hello) however as experience has taught some of those involved, even that can be enough to irritate some people. Is it necessarily fair to voice your opinion in what came across as heated and upset, when it is you who is pushing your own expectation onto others?
I agree that saying hello is a common courtesy from one person to another, however, if I believe that talking to somebody may in fact have the negative consequence of them not purchasing my items, you can be sure that I will smile politely and keep my mouth shut until they choose to engage me. Once again this is based only upon my own experience as your opinions are based upon yours.
I would also like to briefly address the issue of the bitching and moaning (or was it whining?) about creators blaming the crowd for lack of sales or saying that we weren't represented etc. Once again, as somebody who is simply coming to attend the show, you are not necessarily going to be aware of the expectations of the rest of the crowd (which in my opinion was very mainstream - based on the requests of people for well known and publicised titles such as Sin CIty and V for Vendetta). Just because you were there to check out the local material, please don't assume that others were. No amount of greeting and sweet talk is going to convince some 14 year old that he should purchase your small press, independent, self-published and relatively unknown material. It may sound like people are just looking for something to blame other than themselves (and I believe that there certainly is a lot of validity in your arguments for marketing) bet I ask that you look at the entire picture yourself, rather than using the tunnel-visioned approach that you are blaming the creators themselves of using.
Without getting up on a soapbox (or at least trying not to) I think that you need to have sat behind a table before you can understand the motivations of the creators of Artists Alley, or any other convention stand. It really is a different experience to simply attending. When you attend a show, about the worst thing you can say to yourself is 'that was shit' , but if you are there putting your material (and as others have mentioned previously, a part of yourself on the pages of your material) there is so much more at stake. You can walk away feeling like a total failure if it doesn't go well. All the more reason to try harder you might say, but for some people it is such an investment even creating this material (something that may have taken 2 years that some snotty nosed little brat flips through in 3 seconds and turns to his mate and says 'this is shit') that to pour even more of themselves into it, in a completely public forum only to have it rejected is absolutely crushing. We all need to be able to take criticism, and most of us here do take it well, but please understand what it is that we put on the line by attending these sorts of events. I'm not trying to say that we are all needing our ego's stroked to feel good about what we do, but to have somebody who operated from the outside throwing stones without having seen it from the creators perspective (I can only assume this as you have not said that you are in fact a creator) is hurtful and out of place.
The point of all of this is to say that sometimes we may come across as unfriendly or removed, but we we all strive to be the best creators we can be. We are often shy or reserved or introverted. We live through our creations. We aim for those to speak for themselves. Famous people can live off a reputation, unfortunately we must make an impression through our artwork and writing. We are not necessarily salesman, or business people and if we all were we probably would have something closer to an industry.