1. Mac OS X doesn’t know how to stop looping the CrashReporter process on repeated crashing apps.
2. 64-bit Linux kernel doesn’t know how to deal with full swap situation.

But more importantly, given that “100% CPU” situations will arise, why are OS’s designed in such a way that basic user inputs like mouse and keyboard aren’t given precedence at all times? Even just to catch some escape key combo to give the user a chance to correct the offending situation? I don’t believe for a moment that a small amount of computing time cannot be devoted solely to process user input at all times. If your computing resources cannot handle that, then cut out the other crap that’s going on. If the user wants to do something, listen to the user! Simple concept.