I was talking a client recently who was very excited about another one of my sites that she saw.  It was a flash site.  So, I explained to her that recently I try to stay away from flash-based sites.  When we got off of the phone I realized that I've never formally explained why I focus on HTML sites as opposed to flash sites.  That's probably because (albeit subconscious) I really do love flash sites.  I like the way they look; I like the way they move; I like the way they make me feel.  Despite all of that, I stay away from them as much as I can.  And here's why ...

You're Out
People want information nowadays.  They want it quickly.  They want it concisely.  They want it refer-ably.  Flash sites became so popular because they are so impressive and interactive.  That day has passed.  No one is impressed anymore.  You can't scare kids, shock teens or impress professionals.  Flash sites have a tendency to focus less on information while putting an emphasis on aesthetics.  They tend to have poor navigation, make you wait through a scene change for the information to be displayed and shove it all under one web address.

Hidden Beauty
With anything there is a trade off.  Though flash sites are typically gorgeous, they hinder search engine optimization efforts.  When Google searches a flash site it simply doesn't see everything that is there.  It can search hard text, but it can't read ALT text on pictures or TITLE text on links.  Blogs don't fit into them.  RSS is a no go.  Social bookmarking can't be done effectively.  And again, everything exists under one page.

Immobile
The world has gotten smaller.  The internet has gotten so small it fits in the palm of your hand ... on your phone.  Your site can be accessed by anyone anywhere from their mobile device, but not if it's flash.  Steve Jobs was given a hard time when he said that the mobile Apple products wouldn't have flash lite on them, but truth be told the overwhelming majority of Android phones don't have them either.  Blackberries of course can't handle them either (but they don't really count).

Keep it Up
Full discloser: I get to charge a fair amount of money every month for keeping my clients' sites up to date.  It's a little thing we call maintenance, my friend.  However, I give my clients access to make those changes themselves.  I encourage them to do what they can to keep their sites up to date.  I encourage them to blog once a week.  No, I don't make any money like that, but I make better sites like that.  On a flash site one would need the right program and a fair amount of know-how to use it.  Business professionals have too much to do to learn new skill sets just to ensure that their site is up to date.

For these reasons, I say this: Flash sites are like the stereotypical cheerleaders back in high school; they look great, but they are too high maintenance.