Using chatrooms to sting politicians
You can also read coverage of the journalistic issues at the Seattle Times, which includes responses from the Spokesman's editor and professors of journalism ethics. It not only documents the reasons behind the decision, but also the dangers of it amounting to entrapment. It's well worth reading in full, but here's a key quote:
Smith of The Spokesman-Review said ... "I would be lying if I said I'm not troubled by it. It's a step we took with great reluctance," after many newsroom discussions and after consulting with outside journalism-ethics experts.
Reporters and editors asked themselves whether they could obtain on their own the information they needed.
"What we were trying to ascertain was whether the man we were tracking on [the Web site] was, in fact, Jim West [the Mayor]. ... We had allegations from three individuals that they had interacted with this person and that this person was West. But we needed more substantial verification than they were able to provide.
... From the outset, the newspaper decided to explain to readers about the use of the outside expert and fictional scenario but debated whether to publish the chat transcripts. In the end, it did so. "It was only fair that readers saw what we saw to see if we quoted people fairly, accurately and contextually," Smith said.