John Seigenthaler, Sr.
John Seigenthaler was a Tennessee journalist who was also an assistant to Robert F. Kennedy when Kennedy was United States Attorney General. Seigenthaler helped end segregation in the South. Seigenthaler recently became involved in a high-profile controversy after his Wikipedia entry was edited to include inaccurate information and not repaired for four months.
In 1961, Siegenthaler was sent by the federal government to Alabama to help ensure safety for the Freedom Riders. After the Democratic Governor John Patterson had failed to order protection for the Freedom Riders, Siegenthaler stood in front of a mob to protect their safety and was beaten unconscious by the mob despite his warnings that he was with the Federal Government.
In May 2005, an unregistered editor added to the article on Siegenthaler in Wikipedia that "For a short time, he was thought to have been directly involved in the Kennedy assassinations of both John, and his brother, Bobby. Nothing was ever proven." This stayed up for four months until Siegenthaler himself saw it and tried to take it down. Siegenthaler published an account of his experience and associated problems with Wikipedia in USA Today. Siegenthaler then attempted to identify who had made the edit, but was unsuccessful until Daniel Brandt was able to trace back the IP address to a specific corporation whereupon the perpetrator was identified.