2009/1/28 Steve Summit scs@eskimo.com:
Specifically, it took 34 years for a prank perpetrated in the pages of the British Medical Journal to be revealed:
http://abcnews.go.com/Health/PainNews/story?id=6744607&page=1
That was a pretty obvious hoax, though, so I suspect most people just interpreted it as a joke and ignored it.