Copyblogger posted a quote from John Caples, one of the great ad men from the past. He wrote, in 1932:
Don’t make ads simple because you think people are low in intelligence. Some are smart and some are not smart. The point is that people are thinking about other things when they see your ad. Your ad does not get their full attention or intelligence. Your ad gets only a fraction of their intelligence . . . . People won’t study your ad carefully. They can’t be bothered. And so you have to make your ads simple.
While this quote is intended to aid commerce, I think it has uses for art as well. I'm not saying all art should be simple, but I think this quote makes a good case for at least an appearance or layer of simplicity that will allow someone to get something from it without their full attention.
If you are creating something that you want to be read or viewed by a large number of people, especially if it's intended for the web, it needs to be graspable without someone's full attention. The competition is fierce and you're lucky if someone is paying even 25% attention when they look at something you've created. The complexity can be there, under the surface, to reward the people that decide to look deeper, but they have to have a reason to look.
There are lots of places this doesn't apply, but I thought it was an interesting idea. Don't dumb it down, just simplify.