With the recent events  of the internet SOPA blackout of January 19th in mind, this infographic from Socially Aware presents a Social Media law timeline that starts with 1984’s Sony v. Universal Studios –
Wikipedia reads:

Sony Corp. of America v. Universal City Studios, Inc., 464 U.S. 417 (1984),[1] also known as the “Betamax case”, is a decision by the Supreme Court of the United States which ruled that the making of individual copies of complete television shows for purposes of time-shifting does not constitute copyright infringement, but is fair use.

It is worth noting that that in 1998, the Digital Millenium Copyright Act similarly protected sites relying on user-generated content.