Is there such a thing as too much?
Recent (okay not so recent) developments in the area of web development have led a lot of designers to hop on the latest and greatest and slam WAY too much 2.0 into their sites. Sadly, I have to admit that I am guilty as well. Some points to remember as you are AJAX-ing and flashing your site to death:
1) It’s only a good thing if it’s useful to the user and his or her end experience. If you are just adding flashy elements because you can, stop. Go back to some solid HTML or dynamically generated content with you favorite coding language.
2) Search engines are NOT, repeat NOT, going to be indexing your super cool AJAX and, unless you’ve coded it properly, flash elements. Rather than try to explain the specifics around this, know that Google is your friend. Spend some time researching.
That being said, there are times when adding some flash elements or some nice AJAX to a page are certainly called for but be careful that you pay attention to the two points above. I personally love a good AJAX login, voting system, or modal box/light box element shoved in when called for.