Shedding some light on Flash
Flash is Adobe's (was Macromedia) primary web multimedia application. Originally intended for animation now powers simple games and video such as the YouTube videos on this site.
The bottom line on usability:
Adobe tries to make Flash as accessible as possible. It's up to the designer to use Flash in such a way that isn't irritating (don't use entry splash screens!).
More on Usability
Back in 2000, Jakob Nielson said
Although multimedia has its role on the Web, current Flash technology tends to discourage usability for three reasons: it makes bad design more likely, it breaks with the Web's fundamental interaction style, and it consumes resources that would be better spent enhancing a site's core value.
Adobe has made efforts to correct Flash accessibility (and usability) issues since 2000, but Neilen's article title sums it up: "Flash: 99% Bad"
You can see some of the usability issues in Flash at Grant Dickie's and my Educational Unix Text Adventure! If you were to visit that site, you'd notice
- that the text in the Flash object you can't copy and paste. You can make text in Flash copyable, as you can also see in the Flash object. Images also have this problem. For instance, the icons in the upper left hand corner of the screen all have text on them. My guess is no one cares about copying the text on those icons, but on a page like Sibelius Scorch where you might want to copy the name of the program (not easy to spell if you've only seen the word a couple times), there are lots of places where it is named in images and flash. On this particular site, there were text alternatives, but that's not always the case.
- you can't save the file, like you can an image. There are programs out there thatwill do it, but it isn't standard behavior.
So, why are these usability issues? Well, the web isn't just about reading anymore. It never was supposed to be, according to Tim Berners-Lee, who
"Even though the Flash plugin is referred to as "Shockwave Flash", it should not be confused with the Shockwave plugin that handles "Shockwave for Director" content. - MozillaZine
When flash is not installed in K-meleon it looks like:

REFERENCES
Websites
Books
Scholarly Articles
Author Abstract:This study presents the results of a usability test of animated library instruction tutorials developed in Flash using the software Macromedia Captivate. The tutorials demonstrated title searching, author searching, and keyword searching in the University of North Carolina at Chapel Hill University Libraries OPAC. Five participants viewed three tutorials and completed two surveys, one with demographic questions, the other with questions about the design and function of the tutorials. The results suggest that the tutorials are usable in design and function, and all participants reported learning something about searching the OPAC. However, the participants also reported finding the tutorials boring and expressed skepticism that undergraduate students would recognize the advantages of using a search instruction tutorial.