There's a plugin for Firefox that does too where you have to click to activate. It's only a matter of time before Click to activate Flash becomes standard due to all the adverts that keep happening in web browsers.
Actually, 'click to activate' was about to become the standard in IE thanks to MS losing a courtbattle with eolas, which has a patent for automatically running browser plugins... but appeals have been filed again, and the final results aren't in yet.
If eolas wins, expect pretty much any plugin in IE to require a click before activation, since they said they weren't going to be paying the bazillion dollar licensing fee that eolas demanded of them.