See the following link about SWF metadata for searchability:
http://tutorials.lastashero.com/2005/10/using_swf_metadata_in_flash_8.html

One other point about searchability is that it is important to remember the difference between searching content and searching application data. The former is what search engines are designed to do. They don’t really do the latter at all, and that’s a good thing. Let me illustrate this with an example.

Go to google and search for “customize a harley”. The top link will take you to http://tinyurl.com/yev4xu. Perfect. There you’ll see a link to “Build the Harley of Your Dreams”. When you click on it, you’ll start a Flex-based configurator RIA that will visually guide you through the process of building a custom bike. So was this app searchable? Well, not in the traditional sense - Google did not return data from the part compatibility rules engine. But was the app findable? Very.

In most RIAs (Flex or Ajax or Servlets or XUL or XAML), the application initializes on the client is populated with data through middleware layer on a remote server. The application doesn’t contain much, if any data. It is a container into which data is poured via JSON, SOAP, REST, AMF, RTMP, RMI, Remoting, etc.) In this architecture, what is that you want to have a search engine index? The UI of the app (how many data grids are there, how many numeric steppers are there, and what color are they, etc?)? Probably not. Do you want Google to index the full contents of the remote database? Probably not, unless it is a product catalog, in which case by all means, you should put it out there for searching. Is it the fact that the RIA exists - that there is a useful tool that can streamline a complex multi-step process that is of interest to me? Absolutely! Is this possible with Flex/Flash? Absolutely. You just have to think about the *application* in the context of all the *content* that surrounds it. Content is meant to be searched. Apps are meant to be used. Content helps you find useful apps. I think it’s that simple. Let me know if I’m missing something.

6) Accessibility issues for users with disabilities — not just visual disabilities, but hearing and learning disabilities as well, and even motor disabilities

I actually have done some digging recently that shows that’s not entirely true either — but it takes a good deal of work to make that so:
http://www.webaim.org/techniques/flash/

With educational software, especially, you need to be aware of these things, as with public schools and universities, Section 508 may come into play, as well as state-level legislation regarding accessibility for public education…

Flash allows a far greater range of expression than other web canvasses. Flash allows the content creator to express far more emotion and other such human experiences. It is very difficult with HTML/JS to appeal to emotions and such.