@MedicineStorm: There were a number of reasons, I would say the main one was financial problems, they couldn't afford to keep the servers going. On the other hand, they were unable to survive the transition to Web 2.0. Most of the pros started using social media and stopped posting on the forums, and many aspiring artists followed their lead. Last but not least, there were changes in the industry itself with regards to digital art. Photobashing started to become more and more commonplace, almost in replacement of "painterly" characters, evironments, creatures, vehicles, etc. While the pros did make this transition, many of the aspiring artists felt that this wasn't the best way to get better at drawing and painting, so they migrated to other sites, seeking to learn the fundamentals of art before venturing into specific techniques like photobashing. The nail in the coffin was a lecture delivered by an industry figure whose name I can't recall, but the title of the lecture was "Concept art is dead". I think it's on youtube. He wasn't referencing the site in particular, but rather the idea of "traditional" concept art as purely "painterly", and how that idea is almost dead in today's triple A studios.

Here's a very nice article titled "The Rise and Fall of Internet Art Communities". I mentions conceptart.org, but it's more of a historical piece on digital artistic communities in general:

https://www.artsy.net/article/artsy-editorial-rise-fall-internet-art-communities

@Malifer: I wasn't aware of that. Could you elaborate on those points? It's not that I don't believe you, it's just that I never saw it that way. When did you joint conceptart.org? I joined when it was before its peak, as in, when Massive Black didn't even exist, and when Marko Djurdjevic had not been hired by Marvel, etc.
I do think you're overreacting when you accuse me of saying wrong and false things. That the industry did change, and the impact that it did have on artistic communities in general is a reality that few would deny.

Conceptart.org was launched in 2003, that's 17 years ago. I joined in January of 2004, the site was barely 1 year old. Andrew Jones had not finished his first year of self portraits yet, Jason Manley was still doing portraits for Bioware, and nobody knew who Wes Burt was at that point. I remember when they had the workshop in Amsterdam and then the one in Prague, a friend of mine actually went to the latter. I exchanged messges with Marko Djurdjevic, he had some very inspiring things to say. I participated weekly in the Creature of the Week challenged and actually exchanged pencil sketches with Fozzybar via snail mail. I was there when Massive Black was inaugurated. Neither Marko nor Wes were part of Massive Black at that point, nor was any part of the site paid. They did sell DVDs, such as Marko's charachter design course. But the site itself did not have paid sections. I left many years before you did, the site was still going strong, and nobody was trying to cash in on anything when I left, unless you consider selling DVDs as a form of cashing in.

@Malifer: The reason I'm being defensive is not due to my own ego, rather it's because I have cherished memories about that site. While I do have my critiques, I believe that the thing that made it so great was that we were all learning the fundamentals together. Even the pros were learning from each other. I had my own sketchbook, as did a lot of other people, and I joined a sketch group, as did a lot of other people. We would post our drawings and paintings daily, and we would give and recieve cool critiques and tips on how to improve. I never made it past the amateur stage, but I saw some people truly rise and become stars in the industry. People like Justin Sweet, Jason Chan, Bjorn Hurri. I'm not just name-dropping here, these are people whose transformation I saw, a transformation that began with "he's pretty good" and lead up to "he's one of the top tier artists of the industry". And they would share the experience and knowledge that they acquired with the rest of us mortals. Ultimately, I too pursued a different career path, I had to make a choice of what I wanted to do with my life, and I didn't see myself becoming a professional artist, at least nowhere near the people I just mentioned. I got back into art a few years back. My day job is not artistic, but I would like to improve my artistic skills, at least as a hobby. I wish conceptart.org still existed because the things that I learned there were invaluable. I went from literally zero skills to a somewhat mid-level. That may not seem like much, but to me it was invaluable.

Now, one of the things that also must be said is that there certainly was an air of elitism on that site. There was also unnecessary animosity towards other sites such as DeviantArt. However, despite these otherwise unpleasant characteristics, I believe that the good things far outweighed the bad ones. The site was unusually engaing, it fostered active participation to a level that was unheard of. It was a community, in the truest sense of the word. Today's social media are far, very far, from accomplishing anything similar. Yet I think that there may be hope. Sites like OGA are, to some degree, the heirs of those ancient digital communities that were so great back in the day. True, the level of participation is not the same. But I like to think that niche websites such as this one have something to offer that cannot be found on Facebook, Instagram or the like.

There was one guy in particular, I can't remember his name. But he had a sketchbook and his first post was something along these lines: "Ok people, I'm a breadmaker and I'm my forties. I don't know anything about art but I want to learn. I'm going to post one drawing every day, feel free to criticize." 

His first post was a drawing of a cube. Like those cubes that you scribble when you're bored and have nothing else to do. And it was really bad, the perspective was off, the lines were wobbly. So people pointed that out to him and he said "Alright, I'll post a better cube tomorrow". This went on for days, then months, then years. He drew people, cars, animals, clothes, etc. Every time that he started a new subject, it was bad. But you could see an overall improvement. And every time he posted something, people commented on how he could fix this or that thing to make the picture better. After 4 or 5 years, he ended up with a really good level, way better than the rest of us. He selected his best pieces and he put together a portfolio, and he ended up working part time as a freelance artist.

That journey was one of the most amazing things that I have ever seen. I don't know if the guy quit his day job or not, but seeing someone going from zero knowledge to working artist, even if it was a part time thing, was very inspirational.

: O

That looks exactly like what conceptart.org looked like in the beginning! It definately has the same vibe, with the featured artist section, the sketchbooks, etc. Wow. I'll have to check it out in more detail, but it looks really, really close to what I had in mind. Thanks for sharing!