Like polls, we hate or love anonymous sources depending on whether we like what we hear.
Let me give you an example: McClatchy
reported a few weeks ago that President Obama was "leaning toward 34,000 troops." Some people immmediately cast doubt on the report because these sources were "sent by McCaffrey" or were rooted in rumors by unreliable sources. The White House himself immediately jumped and said the President had not made up his mind yet...The result? Obama is sending 34,000 extra troops to Afghanistan.
Now Keith Olbermann is saying, based on anonymous sources (according to a thread here), that the surge will be followed by a withdrawal starting next year. The same ones warning about the unreliability of anonymous sources, those who unrecommended McClatchy's report, are cheering Olberman's assertion as if it's true.
It may be true or not, but it shows you how the human being often clings to what he/she wants to hear.