I almost forgot about this one. There was some controversy over this a few years back. Joe Satriani sued the band Coldplay for copyright infringement. I'm not sure how it turned out ( I think they settled out of court). My personal opinion? Yeah they ripped him off. Big time! In addition, there are many interviews prior to the release of the song where they talked about how much they love Satriani and how he was a big influence on all of them, so they would have definitely been familiar with his songs.
http://www.youtube.com/watch?v=71ccgjAAAqU&feature=watch_response_rev