Love those rock & roll lawsuits! Here's a fun one: Led Zeppelin's Jimmy Page and Robert Plant are being sued for copyright infringement for the opening guitar line on their overwrought classic, "Stairway to Heaven."
The plaintiff is the estate of Randy Wolfe (aka Randy California) of the band Spirit. The estate alleges that Page and Plant—as composers of the song—stole the guitar intro from a Spirit song, "Taurus," that California wrote.
Zeppelin as a band has reportedly made over a half billion dollars on "Stairway to Heaven" and Page and Plant have probably made even more from songwriter royalties, so what's at stake here isn't chump change.
Listening to the opening of the two songs back to back, I think Page's guitar intro may qualify as a lift. [The video I linked to is no longer available.] Page even plays it in the same key (A minor) that Spirit used. Zeppelin was likely exposed to the song when the band opened for Spirit in the late 60s. And the fact that Zeppelin has a history of losing plagiarism lawsuits won't help the case—assuming it makes it to trial without a settlement.