Flash is a nice fancy web technology developed and used over years now. Never the less I try to get rid of it.
A lot of security problems are connected with the use of flash in web browsers. The performance is not the best and it looks like that the big players like Google, Apple and Microsoft are more going the HTML 5 way of doing innovative stuff with the web.
There was a guy already who blogged about using the web without flash some time ago. Now I do my own experiment with it. I will see if the web still is working after I deactivate the Adobe Flash plugin in my browser.
The most web tools I am using like Piwik or Wordpress removed the most Flash based stuff.
Youtube has a html5 project as well. The complete Google tool set never was based on Flash and Facebook ... who cares about Facebook .. we have Google+ now ;-)
Btw. if you want to disable Flash in your Firefox you only need to deactivate this plugin under Tools -> Add-ons -> Plugins: