Wait, this is a thing? There are people think it's ok to use a gizmo that breaks other people's seats?
Knee Defender Passenger Speaks Out About In-Flight Dispute (The Huffington Post)
...When the jet was airborne, Beach took out his laptop to review a contract for his company, which develops waste recycling facilities, primarily in Russia. He used the Knee Defender — a Christmas gift a few years ago from his wife — to prevent the woman in front from reclining.
...
"I put them in maybe a third of the time. Usually, the person in front tries (to recline) their seat a couple of times, and then they forget about it," Beach said. The device comes with a courtesy card to tell passengers that you've blocked them, but he doesn't use it.
"I'd rather just kind of let them think the seat is broken, rather than start a confrontation," he said.