Late this summer, Numero Group, the label of soul legend Syl Johnson, brought to everyone's attention the fact that Kanye West and Jay-Z's Watch the Throne was using an unlicensed sample of Johnson on "The Joy." Read Numero's missive here, but basically Kanye contacted Numero about including "The Joy" on My Beautiful Dark Twisted Fantasy, and couldn't clear the sample, but he went ahead and included it on Watch the Throne without finishing the licensing procedure.
After some speculation, Johnson has gone ahead and sued West and Jay-Z, seeking unspecified damages. Johnson had a monster lawsuit against Cypress Hill that lasted more than 10 years and for a total of $29 million (it was dismissed), so don't count him out here. Compare the songs below via Billboard.