Though limited as a tool for the most effective S.E.O. (Search Engine Optimization), flash animation is the standard for animating a message on the internet. For both size and cost, animation produced using Flash has the best value, and the most flexibility, than any other format.
Hollywood studios and music corporations use flash based web sites for a reason: nothing else comes close to giving a graphic, exciting sound/visual presentation on the internet. Entire web sites are created using flash, offering the kind of graphic interaction not available through standard HTMl sites.
The drawbacks are the limitations of SEO, as search engine spiders are not able to penetrate Flash code effectively to create a thorough indexing of a web site.
Using a combination of Flash animation and standards HTML can allow sites to create a mix of both for a "best of both worlds" presentation.
Below are a few samples of my work in flash animation.