We were taking a circuitous route to Barbados one time due to some cancelled flights, and it was a riot getting on a plane without overhead bins. I had people I didn't know placing things under my seat because it wasn't 100% full. The flight attendant comes in and looks under everyone's seat and starts asking your name, if your name wasn't on the item, she started taking it off the plane. The "owner" was claiming it then, but then it had to go under their own seat. I found it humorous, but it took forever to get off the ground because people had to claim "their own" luggage under their seats.

Really, to make it quicker, they should charge for what luggage people bring on board, give the checked luggage much cheaper rates to make it quicker boarding.