In 2006 (before my time in ultrarunning) there was a controversy at the finish of the Western States 100. Front runner Brian Morrison collapsed a few times in the final 300 meters of the race (inside the stadium at Auburn) and was disqualified because he was helped up on his way to the finish line by his pacers (one of whom was Scott Jurek).
A brief account of the controversy is still accessible on Scott Dunlap's blog.