Is He Crazy?

So, as my readers know, I am part of a brilliant blog network.  One of my fellow bloggers raised an interesting point.  Basically, the question is if his exes are crazy, is he too?

Now, don't get me wrong, I know firsthand that there are PLENTY of crazy women out there.  However, whenever a guy tells me his ex-gf is crazy, I default to blaming him for either a) doing something to piss her off, and she reacted with the normal human emotion of anger or b) having bad judgment in partners (which then opens the can of worms of 'does he have bad judgment in general? does he not have a keen sense of the obvious? etc., etc.)

What are your thoughts?  When a guy says his ex is crazy, do you take it at face value, or somehow place some of the blame on him like I do?  What if there's more than one crazy ex?  Is this red flag of the year?  Did he then pick you cause he's in a pattern of picking, well, crazies?  Has anyone out there dated a guy with a 'crazy ex' who turned out to be totally normal?   Do normal, functioning members of society sometimes just go crazy on a dime, or did they always have it in them in the first place?!