Flash makes it possible for web designers to put fancy animations and advanced multimedia into their sites. The problem is, it may look good but it can make a site slow to load and hard to use, especially in the hands of the inexperienced. Flashturbation may win design awards and look cool, but it generally chases away web surfers. Many surfers are turned off by it, and will leave your site if you indulge in it. Nevertheless, it is seen everywhere, but especially at the web front doors of graphic design studios and advertising agencies.
Most web surfers have to take things slow.
They don't have high speed connections, and they don't want you to ram your bloated site down their throats. They like a site to work with them. They like a site to entice them in, and to encourage them to explore. Surfers don't want to get Flashed at the front door to your site, even if you ask them if it's ok. Surfers don't want to go to a site that looks cool.