Not sure where I first saw this, but the WebKit plugin ClickToFlash is a required for any Safari user. Flash has numerous bad properties. It’s a resource hog and many sites use it for annoying things like ads that start playing once you navigate to a site. ClickToFlash intercepts all that and gives you a simple button in place of the Flash content. If you do want to view it, click the button.
There is also a nice whitelist feature you can use to enable entire sites to run Flash without permission. Additionally, it is easy to turn off ClickToFlash if you really need to.
Rumor is that this was originally written by someone in Adobe but no idea if that is true. Jonathan ‘Wolf’ Rentzsch is the current maintainer of it now. Code is available on GitHub. And it’s not an InputManager hack so it looks like a real solution.