In 2007, the cute baby above was at the center of a copyright lawsuit with big implications. The video, posted by Stephanie Lenz features her kids dancing along to Prince's "Let's Go Crazy." Universal Music Group demanded that the video be taken down because it infringed on Prince's copyright under the DMCA. The ensuing court battle was long and arduous, reflecting a key question for platforms like Youtube which, at the time, were becoming increasingly commonplace.
Today, a federal appeals court sided with Lenz, whose children are now in the fourth grade, saying that copyright holders have to prove a song was not in "fair use" before they could demand it be taken down. There's a four-pronged test that judges consider when determining whether or not a song is fair use: "the purpose of your use, the nature of the copyrighted work, the amount and substantiality of the portion taken, and the effect of the use upon the potential market." The ruling comes as Sharebeast, a site that poked at other questions of copyright law, was shut down.