One of the oldest topics in SEO is how can I optimize my Flash site for search engines? Honestly, the sad answer has always been, you can't optimize Flash pages to do well in search engines. Of course, there are workarounds, but those workarounds are suggestions on how to make use of Flash alternatives to create the same thing.
Kim posted a Cre8asite Forums thread asking, what should one do when a client requires Flash and also requires the site to rank well in search engines.
Now, let me step back... A Flash site can rank well in search engines. Search engines use many factors in ranking a page, one factor which is weighted heavily is link analysis. So a page with many links can rank well, even if the search engine cannot read the text on that page. But the bottom line is that Flash pages are not "search engine friendly" because spiders have trouble crawling, understanding and indexing the content on those pages.
The Google help documents has a Q&A that asks Does Google index sites that use Macromedia Flash?
Yes, Google indexes pages that use Macromedia Flash. However, our crawlers may experience problems indexing Flash pages. If you're concerned that Flash content on your pages may be inhibiting Google's ability to crawl your site, you may want to consider using a text browser such as Lynx to examine your site. If features such as Flash keep you from seeing all of your site in a text browser, then search engine spiders may have trouble crawling your site.Also, the Google Webmaster Central blog has some excellent advice on the topic.
You may want to consider creating HTML copies of these Flash pages for our crawler. If you create HTML copies, please be sure to include a robots.txt file that disallows the Flash pages in order to ensure that our crawler doesn't recognize these pages as duplicate content.
Finally, you might consider creating and submitting a detailed site map of your pages using Sitemaps. Sitemaps are an easy way for you to submit all your URLs to the Google index and get detailed reports about the visibility of your pages on Google. With Sitemaps, you can automatically keep us informed of all of your current pages and of any updates you make to those pages. Please note that submitting a Sitemap doesn't guarantee that all pages of your site will be crawled or included in our search results.
The folks at Cre8asite Forums recommend using the SWFObject if necessary.
My advice, and it is mentioned in the forum threads, use Flash elements within the site but do not use Flash 100%. Do not use Flash for the complete site, do not use Flash for the main navigation or main content area.
Forum discussion at Cre8asite Forums.