Don't forget about SeatGuru (http://www.seatguru.com), a TripAdvisor company, which specializes in collecting and curating exactly this kind of data. They're not exactly n00bs at this kind of thing…
And that's the hard part. It's even worse for the more common case of domestic flights, because those get swapped way more often than long-haul international.
The market is not working from consumer point of view, becsuse you don't really know what you are getting when booking the ticket.