Hello.
I would like know if is possible to know who buy our photos and what for what purpose?

Thanks

Use Google Reverse Image Search.
If you use Chrome browser, right click on an image you have sold and choose 'Search Google with this image' and see what you can find. It doesn't turn up everything, and of course you'll have plenty of uses in print only.
If you don't use Chrome, you'll need to get a plug-in, but I just keep Chrome for this purpose.

I only recently started doing screen saves when I find my images in use. I use Google Reverse Image Search to find them now.  I recently found an image as the cover of a romance novel and 2 other images as covers engineering reference checks. I once had the Humane Society use one of my images and I never saved it. I found one being used for Nat Geo Brasil. Hey I am a National Geographic photographer and they didn't even invoke me into the Explore's Club! I think I got about 7 bucks for that one, a photo of a falcon in flight in an article about fastest animals. So many corporate brochures I don't even bother to save them anymore. Another one I found in my US mail when it was used in a trade magazine as the center image in a promotion for the International Workboat show.  I never get credit, not even Nat Geo.

The Google Reverse Image Search is the way I used too.

But every time that I searched where my images have been used I found some that have probably been stolen.
This made me feel so bad�

Now I prefer to ignore what happens with these images.
I have stopped to search them� and I feel happy!

Use Google Reverse Image Search.

this will only work for images embedded using the IMG tag in HTML.

but i'm seeing lots of and lots of newspapers displaying images and especially slideshows using CSS tags, Javascript, and Flash.

none of these images will be indexed in google images.

Excellent Pics! much success to you