I agree that flash is an unstable piece of garbage on anything except Windows. Even on Windows, its a pig(in execution -- in installation, it's remained surprisingly tiny!). When they ported it, they seemed to rip out all the error checking -- one gentoo user managed to solve most of his flash crashes by installing every possible font. On Windows, it doesn't draw fonts it doesn't have, everywhere else, it just dies. I'm tempted to recompile Freetype with debugging to track down exactly what missing fonts Flash usually throws tantrums over.

It's also a software of much exploitation. It's frequently abused to cause unblockable popups. It can startle you and your co-workers with unexpected speech. (what moron decided talking ads were a good idea? You leave the page FASTER!) It's a frequent culprit for hogging the sound device, even when it's not playing anything. And when's the last time you saw a flash ad raging at anything but cpu-burning bleeding-edge maximum FPS maximum quality alpha blend gradient?

It's also seemingly airtight in a few important ways -- it may lag, freeze, popup, or crash your browser, but I've never heard of any crackers obtaining filesystem access through malicious flash. It also provides content providers like youtube and internet radio the faux-security of an application layer between the browser and the data stream. (The new flash-less iphone support on youtube has become a hole through which people can download and save video arbitrarily.) It's extremely useful despite all its faults... Therein lies the problem. Which is conveniently defined by the manufacturer as however long they feel like supporting the thing.