A Google Groups thread explores whether Flash websites could be detrimental to search engine optimization efforts.
Bergy of Google offers some feedback and addresses common misconceptions.
For one, he goes into some of the concerns regarding hidden text. You should consider intent, and if you're hiding unrelated keywords, that's spam and should not be practiced. Flash developers often find themselves having to hide text behind flash animations, and as long as the same text is presented to the user and search engine, the rankings should not be affected.
The goal of our guidelines against hidden text and cloaking are to ensure that a user gets the same information as the Googlebot. However, our definition of webspam is dependent on the webmaster's intent. For example, common sense tells us that not all hidden text means webspam--e.g. hidden DIV tags for drop-down menus are probably not webspam, whereas hidden DIVs stuffed full of unrelated keywords are more likely to indicate webspam.
Bergy also reviews the webmaster's site and offers important tips regarding Googlebot's crawlability for specific links. I thought that this is important to share as well:
Googlebot deals with #anchors differently than ?arguments. Googlebot treats ?arguments as strict part of the URL string, but ignores #anchors, since in normal HTML, they all point to the same page...
Therefore, if you have a page that is www.example.com/index.html#aboutus, Google is really only sending PageRank to the index.html page, not the #aboutus anchor.
Forum discussion continues at Google Groups.