A sentence in an Associated Press story about the plane crash that killed former Sen. Ted Stevens of Alaska stopped me this morning:
Stevens became a protege to the younger O'Keefe and they remained close friends over the years.
The writer probably meant that Stevens became a mentor to the younger O'Keefe. Sean O'Keefe, the former NASA administrator injured in the crash, would have been the protege in the pair. This is actually a somewhat common problem for editors to watch for: Writers use an antonym for the word they want.
Another example that I have seen more than once is ancestor-descendant. In describing a contemporary person, a writer refers to him as the "ancestor of a Revolutionary War soldier." It's actually rather easy to overlook this in revising or editing; your mind tends to accept the word because you get the meaning, even if it's the opposite.