What happens when you clutter your desk with so many good things? It will start looking bad, no matter how good the things are individually. And thus the same will happen with your site. Using too much of flash animation will only clutter your site and thus it not be a very good for SEO.
Now the question comes, what exactly is SEO? SEO is nothing but how your site will get ranked in the search engine, when someone searches for it, according to its natural algorithm. SEO actually stands for Search Engine Optimization. It is the process by which the site’s visibility in the search results of the search engine using its own organic elements. This easily translates to more viewers to your site as the higher up your site is in the search rankings more will the traffic that comes to it.
Cluttering your site with too much flash animation can have a lot of problems. The first problem that the visitor might face is that your site will take too long to load. If this happens then the he will get bored and frustrated and will just go to another site. You might think that the animation makes it look good but it would just be a problem for the visitor. The continuous background sound that you might put on the flash animation can also be annoying to the listener (especially when he is surfing the net from his or her cubicle) and also monotonous and thus the visitor will only get bored. The most important reason why too much flash shouldn’t be used is that most of the search engines are not properly able to index and crawl the content of the flash movies and this means that your site may not come up in the ranking even if it was supposed to.