On a similar note, I was waiting to board a US flight yesterday morning at LGA. The shuttle area was pretty packed, but I found several empty seats. One of them had 3-4 used tissues in the seat, so naturally, I took the one farthest away. I didn't pick up the tissues because a) I didn't know what was in them and b) I had no tissues of my own to pick them up with.

Moments later, two older women came over, saw the tissues, picked them up, and deposited them on top of my bag, which was on the end table--not taking up a seat. I burst out "Hey! That's not nice!" but they turned their backs, sat down, and began chattering in rapidfire Italian.

Passing the litter on is a new one for me. I picked up my bag and let the offending snotty bits fall on the floor. I am normally unable to litter, but in this case, I wasn't willing to play janitor.