Defined in the internet draft “A New HTTP Status Code for Legally-restricted Resources”. Intended to be used when resource access is denied for legal reasons, e.g. censorship or government-mandated blocked access. Likely a reference to the 1953 dystopian novel Fahrenheit 451, where books are outlawed.
Andrei Taraschuk and Aaron Ott created a fascinating visualization showing how people on Twitter reacted the Internet blackouts on January 18th in protest of SOPA and PIPA by mapping tweets mentioning #pipa #sopa and #blackout.
(Via Laughing Squid.)
(via Joy of Tech)