I don't mind if the person sitting in front of me on a plane leans their seat back. But some people don't like it. Virginia Postrel offers a good solution:
Instead of giving all seats the right to recline, divide the plane laterally, with reclining seats on one side and non-reclining seats on the other. Those of us who don't care about leaning back and would rather not have other people in our laps could then pick the non-reclining side.