This is almost certainly a floating flight spoiler. Flight spoilers typically are operated by only one hydraulic system, as opposed to two for the ground spoilers. The float occurs when the actuator bypasses internally, allowing the low pressure to lift the panel. The amount of panel lift is in direct proportion to the lift created by the wing (and thus low pressure) and is not really related to airspeed. On a Boeing there is no mechanical device to hold flight spoilers stowed without hydraulic pressure, unlike DC-9's & MD-80's. Since the spoiler panel is raised, a loss of lift occurs, which requires a counter input to keep the wing level.
The amount of aileron deflection appears to be a lot, but remember that it's an inboard aileron without much roll-inducing horsepower. The opposite inboard aileron wouldn't show nearly this much deflection due to the assymetrical travel of ailerons... the downward aileron always travels further than the upward aileron. Chances are that the upward-travelling aileron still appeared faired. This plane is going to burn a lot of extra fuel in this condition, especially on a long flight!
This is almost certainly NOT an example of a misrigged flight control because of the onerous double and triple-checking and inspecting that accompanies rigging procedures. Even more attention to rigging is paid these days due to fuel costs. On top of that, an error in rigging of this magnitude is pretty obvious!
My $.02 worth from an Boeing-qualified airline maintenance instructor, although not a 747 instructor.
