Quick question: What could you do faster? Teach someone how to win a game of solitaire:

Or solve a Rubik's Cube?

Clearly, solitaire is a much easier game to comprehend since the rules are almost immediately obvious. A Rubik's Cube, by comparison, is much more complicated and takes more advanced problem solving strategies to master.

To me, this is similar to the difference between serving websites using HTML vs Flash. HTML is to Flash what Solitaire is to the Rubik's cube. In this case, the person who needs to understand the game isn't a person at all, but a search engine.

If you think it may be valuable for search engines to be able to read the content of your site, understand the navigation, and rank it competitively, do you think you're better off building a site with a solitaire styled structure or a Rubik's Cube? The same information could be presented in either form. But which one will be easier for search engines to comprehend?

Search engines, including Google, have made some recent progress in their ability to index Flash sites. That's a good thing for people trying to find content that web designers have chosen - largely unintentionally - to hide. But it's not nearly as powerful as what they can do with more traditional presentations of data on the web.

Rand Fishkin has more on why Flash remains problematic for web design on SEOMoz.