Originally Posted by hindle

A few years back I was on a 737, sitting in the bulkhead row in seat A. No surprise, all of the overhead bins in the front of coach were full with the doors closed already. The person in seat C had gone to the bathroom at this point.
Some clown comes on board, opens the bin above me and proceeds to pull Mr. C's briefcase down and puts HIS bag in the same spot. I confront him and ask why he's moving other people's bags onto the floor without asking and he gives me a rant about how he's paid for his ticket and he has the right to this space as well. I decide to not escalate the situation and let him go about his business as he re-closes the bin and walks to the back of the plane.

45 seconds later, I get up, take his bag out and put it on the ground (mind you, he just left Mr. C's briefcase sitting in the aisle and just walked away), and then put Mr. C's stuff back up top. When the FA comes around asking who's bag was sitting on the ground, I explain to him what had happened and he gladly found the offending passenger and checked the luggage for him.