We all know that's not possible. That would be like Firefox blocking requests to facebook.com because some users end up getting phished or stuck with malware from facebook apps. Nobody would use a browser that blocks flash (and doesn't support h.264 in <video>).

If I remember right, this was right before Firefox 3.6.4 introduced out-of-process plugins so Flash has its own process to crash instead of taking down the whole browser.

Of course, for some reason the Skype plugin is still capable of crashing it...

That's because it's an extension, not a plugin.

The Skype plugin adds much less functionality to the browser than flash.