What is it with overhead bins?

Some people just don't seem to understand that they are to be shared by everybody sitting in that row of seats. And, while you might think it would be a little better in 1st class where you are dealing with a more sophisticated traveler, the truth is that I have observed even more space abusers up front than in coach. (I know the seats are expensive, but not enough to buy the whole plane, or even the whole row.)

I'll admit I might be a bit of a packing efficiency nut, having spent decades in the trade show exhibit industry, but many travelers, just have no clue whatsoever.

Here's an example. Last week I was running late for an early morning flight. As I ran onto the plane (last one to board)the FA said, "As soon as you are seated, we'll close the door". I opened the overhead bin above my seat (2/A) to see a briefcase lying flat (long side to the aisle) next to a relatively small carry-on lying flat (long side to the aisle). To expedite departure, I flipped both of them up, and turned them in short side to the aisle to accommodate my bag. Just then Mr. 2/B (whose feet didn't even touch the floor, let alone extend into the space under the seat in front of him) said "Will you please not touch my things?"

Well, I am usually a fairly patient human being who at least passed Tact 101, but that morning I was not in the mood for dealing with a prima donna, and my mouth went before my mind and said, "You know, if you really don't want people to touch that stuff, maybe you should leave it at home". (I think I learned that kind of talk on Webflyer.)
Needless to say, this did not begin a relationship where we would be happy to die in one another's arms in the event the plane went down.

When I used the bathroom after a quick breakfast, the FA who had observed this encounter asked, "Are you a flight attendant? If not, you should be, you'd be great." Not anxious to return to Mr. 2/B's sunny personality, I spent the rest of the flight with the crew, listening to their stories of poor bin packing practices. They concurred that the inefficiencies seemed more pronouced in 1st class.

Does this just happen on flights I'm on or is this a common problem? Should all airplane tickets include "How to Share the Space Instructions"? Am I just over-reacting?