I'm the idiot who recently engaged in drunken PDA while in a couple Bars...not exactly light work either.
Not proud of it, but at the time, thinking things like "Hey, what if that person over there just lost their lover" or "That guy/girl may have self esteem issues far exceeding my own and are currently either incapable, lack the gumption, or lack the sheer dumb luck to be in a situation mirroring mine" didn't exactly take precedence.
In retrospect, it should have been toned down significantly, but what the hell? It was fun.
Now, if I KNEW someone next to be had just lost their mother or something, that wouldn't be happening, sober or not, yet that's more a matter of respect than anything else.
So, basically, it all depends on the situation and the people involved. Your sphere of existence. Your prerogative.
Side Note: Golden Rule applies.