Via Google blog
Google has been developing a new algorithm for indexing textual content in Flash files of all kinds, from Flash menus, buttons and banners, to self-contained Flash websites. Recently, we’ve improved the performance of this Flash indexing algorithm by integrating Adobe’s Flash Player technology.
In the past, web designers faced challenges if they chose to develop a site in Flash because the content they included was not indexable by search engines. They needed to make extra effort to ensure that their content was also presented in another way that search engines could find.
Now that we’ve launched our Flash indexing algorithm, web designers can expect improved visibility of their published Flash content, and you can expect to see better search results and snippets. There’s more info on the Webmaster Central blog about the Searchable SWF integration.