He is very careful, or is he? SPOILERS!!!

I would imagine it would be a wise move to wear one. I was wondering about that scene early on in the snow when he shoots that guy in the woods and he falls down near them and he goes right over to the dead guy....never once checking to see if there were any more guys up there with guns.

He probably didn't intend on being shot at. Since the gun he predicted would be used against him was designed to kill the assassin.

And if she was going to use a different gun to take him out, she'd probably be aiming for his head anyway, so a bulletproof vest would not have helped.

So unless you want him to walk around all the time wearing a bulletproof vest, I doubt he would have been prepared. There's a difference between being careful and omniscient.

Yes, and I'm quite there are a plethora of locations in the Italian countryside where one can quickly acquire a bulletproof vest, when one deciphers over a matter of a couple days that he is the intended target of an assassin.

agreed, a meticulous assassin like him would have worn a vest. It doesn't matter if the other guys aim or shoot at his head, it's about covering your bases...and he should have had a vest on...
quite frankly, the producers left it wide open for a sequel and Clooney's character the ability to have that 50% chance of surviving. I for one would hope they don't do a sequel, but you know Hollywood, and if they do, I hope it's done right and not just another sequel krap job

A "bulletproof vest" can usually stop a pistol round, but not necessarily a jacketed rifle round.

If you are shot by a sniper with a rifle, a kevlar vest might not really help you - plus, even if it did, a sniper could just get you with a headshot...