Late last year, David Rohde of the New York Times was kidnapped in Afghanistan and, in order not to increase his worth to his captors, the NYT worked with other news organizations to keep the news secret. Another source that agreed to keep it secret was Jimmy Wales, head of Wikipedia. The details - at least from the NYT side of things - is in "Keeping News of Kidnapping Off Wikipedia" by Richard Perez Pena (link).

There certainly is a strong moral side to this issue, but at the same time it's highly doubtful that Wales would have done the same for a reporter from, say, CNS News or for an independent such as Michael Yon (who told the truth about the story, link). And, as others point out, the NYT hasn't been shy about releasing sensitive information on those who are not employed by them.

However, to concentrate just on the Wikipedia-related aspects, this incident shows yet again that you cannot trust anything you read at that site. In this case, Wales admits that their very special rules - including their "Reliable Sources" rule (WP:RS) - were used to keep something they knew to be the truth out of an entry.

Two news agencies - both with their own brief entries at Wikipedia, and including one established in 1963 - reported the truth about this story, but Wikipedia didn't consider them to be reliable sources.

In other words, the two news agencies reporting the truth were, according to Wikipedia, not reliable sources. At the same time, the New York Times - which was not reporting the truth - was, again according to Wikipedia, a reliable source.

You cannot trust anything you read in Wikipedia.