Toothpic: Who took this picture?

Managing photos over the Internet is an increasingly bigger problem with sizeable social and financial implications. More than 1 billion Facebook users upload in excess of 350 millions of new pictures per day and 250 billions overall, not to mention other social media sites such as Flickr, Instagram, Google+, Tumblr and Pinterest, and these figures are growing steadily. It is hence not surprising that a huge problem has arisen for the users and social media sites alike: it is very difficult to track down a wide range of improper uses of the photos, such as exploiting them for commercial purposes, re-posting others' photos without consent or infringing copyright, posting photos containing unethical or illegal contents, and so forth. To quantify the magnitude of these issues, consider that social media company The Content Factory reportedly got sued $8,000 for using an image on a blog post that got less than 100 visitors. Pinterest's users are held responsible for the pictures they post or re-post, plus they automatically grant licence for reuse on Pinterest. Since many of Pinterest's 70+ million users arguably do not own these rights, they may greatly suffer from legal actions, and this may in turn disrupt the service's popularity.