I don't have business numbers, but there are huge amounts of successful games on the web, using Flash (for example FarmVille on Facebook, etc.).
The issue of course is that Flash has many technical issues, doesn't work in all browsers/all OSes, and so forth, hence the move to do the same games in HTML5.
azakia, a Flash App once requested my permission to turn on my Mac's built-in video camera and microphone.
Funny how I was just then commanded by G-d Almighty Himself to unstall my Flash plugin.
While Flash does require permission to enable video and sound input, I am dead certain that someone with a clue could find a way to do so without actually asking permission.
It's not like those who like to hang at Websites of Ill Repute are diligent about keeping their patches up-to-date.
The issue of course is that Flash has many technical issues, doesn't work in all browsers/all OSes, and so forth, hence the move to do the same games in HTML5.