Also note that for an unstable graphics driver, the way you usually crash the system is by touching memory you shouldn't (through the rendering API), which is definitely something that could be exploited by an attacker. It could also corrupt pages that later get flushed to disk and destroy data instead of just annoy you.

Though I am skeptical as to whether it would happen, security researchers have previously come up with some truly incredible browser exploit chains in the past, so I'm not writing it off.