It's not just SEO. We've seen this pattern play out over and over: Google Adwords were once a gold mine and dirt cheap.
Facebook business pages had many early success stories until Facebook changed the rules. Facebook ads were once effective and affordable until they became expensive.
There were people who became famous on Youtube. Heck, even Myspace was a great platform at one time, before it became filled with spam and then imploded.
This idea applies not just to platforms but to sales and marketing techniques. Think about this: Free shipping for online purchases used to be considered a huge innovation. Now, most people won't buy online without free shipping.
Bringing it home to the art industry: Remember Duane Keiser, the artist? He got famous as the father of the daily painting movement with his blog A Painting a Day. He was even featured in an article in the New York Times. Nobody was doing daily painting in 2004 and it was incredibly successful for Duane Keiser. Now, it seems like everyone is a "daily painter" and there's really no innovative excitement around the idea anymore. [2]
The cutting edge becomes expected.
Game changers become table stakes. And this has convinced me that often, the best marketing ideas are those that other people are ignoring. In fact, if you hear the phrase "best practices" get nervous, because that means you're doing something that has been done by so many people, so many times that somebody made a list of "best practices." Which means it's not an area being ignored.
The good news is that this just means you need to do things a bit differently. Well, you're an artist! Creative and different are what you specialize in!