Find duplicate content on your website or track marketing efforts (eg. infographics).
Find loved ones, lost friends and old flames by searching for their images.
This can include dating sites, social networks and even public forums.
Discover your favorite celebrity names.
If you've found a piece of art that you really want, you can do a reverse image search to find out who the artist is.
If you have your own images that you sell. You can do an image search to see where else on the internet they are to make sure that you get your royalties.