Flash site can be ok for SEO, if there is text supporting them. I recently had a client that wanted two sites done. One of them he wanted done in flash so I referred him to a flash expert. The site I was to do, wasn't needed for a few months. So a few months later I got to work on the non flash site, and not one week later my site was already drawing more search engine traffic, and on a less popular topic. The only reason you should use flash is because your target audience expects it. You can still optimize a flash site for SEO, but unfortunately it not SEO you can do on your site. It involves money, and buying publicity.