We wrote last week about how many people avoid Flash for SEO reasons. The main reason being that Flash is good at showing text to the user when they visit the site, but when Google sends their spiders they can't always find it. If Google can't find your text then your chances of showing up in the search engines for your keywords are greatly diminished.
For this same reason you should always place ALT tags for your graphics. This way the user sees the picture, with any text or description within it, and so does the spider sent out by Google. The more your site caters to both of these visitors, the better your rank will be.