The most relevant current example is Coldplay vs Satriani
http://www.youtube.com/watch?v=UvB9Pj9Znsw
Satriani melody/chord progression just about identical to Coldplays smash hit off of their last album. Coldplay's up for a Grammy for it too, ouch salt on the wound. Coldplay denies it, but come on, that one is just way too close to deny. We're talking Ice Ice Baby / Under Pressure close here.
I remember being in the studio with Eugene McDaniels' and his co-producer when he cut his comeback album and she (co-producer) was telling me if you want to be a songwriter expect people to steal at least a few of your songs! Hmmmm
Anyone have any other examples?