I've never noticed it used as an excuse, and to me that seems a lot like saying "I was biased!", to cast away blame. Though I have a different frame of reference - here you're accountable for anything you do, sober or drunk, including making mistakes/looking incompetent. Where is the line drawn where you can just shrug off any blame? I can't think of any rational reason to want to drink, then, unless you want to... Act incompetently and get away with it? Is this then a good thing?

I agree on the placebo bit, anyway.