You know you can search for images on Google. You can, for example, type in “red Ferrari” in the search box, but click on images to find pictures of red Ferraris instead of links. Well, now you can search by using images. The video above explains it best. Just upload your image and Google will find similar images.
I wonder what implications this has for photographers. Can you use it as a reverse image look-up to see if your image is being used somewhere similar to Tin-Eye or other services I wrote about here. I might be over-thinking it. What do you think? How would you use this feature?