I recently had a flight where my domestic F seat had a broken recline lock. Its a very curious feeling on takeoff to feel oneself slipping backwards into a reclined position as the plane takes off.

During the flight the seat refused to stay up and kept slowly reclining to the rearward stop. I ended up spending most of the flight in the fully reclined position: unfortunately for the person behind me who was trying to do work on a laptop... but it worked out for me as I had wanted to sleep on the flight anyway. I generally feel that recline is the prerogative of the person sitting in the seat not the person sitting behind, so I was glad that the non-working seat lock avoided a potentially awkward "negotiation" with the person behind me.