Does a system exist that can bulk process satellite data to find a plane lost over ocean?
Update: Satellites were eventually used in the search for MA370, see this article.



This question might be better answered by the folks at space exploration but here's a shot:


Oil slicks are not uncommon at sea, so finding one from the aircraft is not too easy.
It's an incredibly large area pulling a lot of processing power. You're going to need pretty good resolution imagery over several square kilometers and then run image recognition on it. Look at this image which has a scale of 25 miles which is still a fraction of what you would need to get an idea:





The fragments you're looking for are very small in regards to waves. I suspect depending on where you are there's a large amount of noise from other rubbish which is hard to filter out, such as a white plastic sheet to a door. You might even go confusing big aircraft parts to other white boats. Yes, you can continue the search but it takes time to go through all of these and dismiss them.
A lot of volunteers searched for Steve Fossett when he went missing, and there was some attempts to locate him by satellite imagery from google maps, which was not successful.
Aircraft, while not fast, can be over the side within a few hours, while I think you have to wait until the satellites have caught all the imagery you would like.


While I think it could be done as you say, you would need to develop software and I don't think the market for it exists, but that's just my guess. Reading up it appears that satellites are used against drug cartels along the USA-Mexico border and against illegal immigrants elsewhere in the world.