Even though search engines can index some SWF content, it still takes special strategies to make the content more visible on the web. One of the most popular websites, YouTube, uses a SWF-based video player, and is extremely visible on the web. Part of the site's success in terms of visibility is attributed to its HTML and other content on each page that work together to effectively to make the SWF content more visible to search engines. So, although a YouTube video may have very little searchable text, search engines know what's in a video based on its HTML title and description. At least at this point, search engine optimization (SEO) is less about making your SWF content visible and more about using effective, searchable HTML to make the content within your SWF easy for search engines to find.
source:
http://www.adobe.com/devnet/flash/ar...seo_flash.html