Lawrence Lessig is a Stanford law professor, and one the leading authorities on the issue of copyright. He is a founding board member of Creative Commons, an organization (and a license name) devoted to making creative works such as images or video available for others to build upon and share. This wonderful TED presentation, in “Lessig Method” style, is about how our culture has been changed (and is changing) by Internet, and why the existing copyright laws are inadequate any more.
Original video on TED.com (might be better quality).
Lessig has been extremely politically active and is widely recognized by the Internet community as having greatly contributed to the freedom of expression. Here’s a “Tribute to Larry Lessig” from Brave New Films, the guys who brought you The Real McCain, FOX Attacks! and Meet the Bloggers: