In the new and ever changing world of the internet there is always advancements made. One advancement that has changed the look of websites as we know it, is the introduction of Macromedia's flash technology. This new technology can integrate movies, pictures, sounds etc. that HTML could not (it can but, HTML is much bigger and chuggier than some of the big presentations). Flash integrates all these into one presentation that is quite small. The same page in HTML would be very chunky, and slow.
Basically Flash is used to make websites look more colorful, have more movement, have music and sound interaction plus much more, but in a smaller neater package. Unfortunately there is a downside to this. The downside being that flash presentations are all packed up into one file. So, the HTML page has to reference this "one" file which basically acts as a movie (movie's are embedded into HTML much like Flash).
As the flash presentation is just the one file, if this is used to surf through your website, then there will be no information on the HTML page, except for the reference to the Flash presentation. This causes problems for having no content (see the small amounts of content page). If there is no other information on the page to index, then spider's will most likely ignore the page. Search engine spiders are unable to "look into" Flash presentations. The same as spiders are unable to look into pictures to tell what it is about. Also the same as looking into a movie. You have to remember that search engine spiders are not "people", they are programs written by "people" to make their job easier.
One thing that goes against what I have been saying here is that the google spider has been able to successfully index the out-bound links from a website. This is the only information that the spider can gather however. The spider looks at the .swf file (flash presentation) in binary format, where you can see the out-bound links if any.
NOTE : Binary is a way of looking at a file. The outbound links of Flash presentations are stored in plain text within the presentation. Therefore, looking at the file in Binary will show these addresses.
So one of the search engine spiders can index some information inside a flash presentation, but it will be unlikely that they will be able to index text from the presentations.