On Nov 20, 2012, at 2:54 PM, Kyle Banerjee wrote:

> My real question is whether anyone has come up with a really good way to
> assign metadata to thousands of photos, preferably in batch fashion? Thanks,

There's a whole field of what they call 'computer vision', which is
basically looking for things in images.  (face detection is just a
small subset of it):

Most of the ones that I know of work with very constrained images
(they're all pictures of the sun, at a known pixel scale, so they
know what size/scale the items are that they're looking for)

The various 'find similar image' engines might be useful to do
some sort of clustering of the images to make them easier to
process.  (eg, extract landscapes vs. buildings vs. people)

Wikipedia has a list of various implementations: