One of the most amazing problems that cannot be solved by computers is – identifying the type of image .. necessarily a particular label for the image.
That is a particular image represents a – desert / barren land / moon surface / ..etc etc.
so, what does google do ?
CroudSourcing Know this ?
Worth a look !
it makes people play this as a game and thus come up with a great solution !
It achieves this by hiring these unknown people ( users ) and making them label the images..
Possibly saving time ! and having their work done for free .
And how does it really help is .. probability is that when two users suggest a same label for the pic.. it has to represent that !