"This practice of passing other vehicles traveling in the same direction by sharing their lane is called lane-splitting, and a new report by UC Berkeley transportation researchers finds that no matter what some angry drivers might think, it does not necessarily pose a greater risk for injury."

http://feeds.boingboing.net/~r/boingboing/iBag/~3/DVwt-vPFzGM/motorcycle-lane-splitting-deem.html