Once, a very beautiful, very drunk girl came out of my favorite watering hole and asked if she could try my pipe. Pretty much pulled it out of my drooling mouth and stuck it right in hers. I was in the process of getting rather excited when her large, off-duty cop husband came out to join and she shoved my pipe in his mouth and told him "taste this, it's really not weed"... First time swabbing a mouthpiece and draft hole with listerine.
Another time, a very pretty young lady came out of the same bar, sniffed the air, and said whatever is in my pipe smells just like what her grandpa smoked, and reminds her of when she used to sit on his lap as a child. I grinned and said "Your grandpa obviously had good taste, but are you trying to hint that you want to sit on my lap?" To my astonishment, she said "Hinting? No, that's exactly what I'm saying!"
Then she did. Then her friends came out and asked what the hell she was doing. Then my girlfriend came out... and there was much 'splainin' to do!!!
There have been a couple times that dudes have asked to "hit" my pipe. I'm just like, "Nah man, that's gross. If you really wanna try it, hmu tomorrow and I'll give you a pipe and a few blends to try, but it's not f'n grass so passing it is just weird."
I guess my point is, not all interruptions are created equal.
I've found the best etiquette, for pipes smokers or anyone else, is just:
~Don't Be A Dick~