The indictment dates the first instance of lying to the [FBI] investigators on October 14, 2003. Patrick Fitzgerald was not appointed as Special Prosecutor until December 30, 2003. Investigators had already spent three months speaking with witnesses who contradicted Libby's account.
....Fitzgerald didn't go on a hunt for administration blood. He did not lay perjury traps. He walked into an office and was immediately presented with some damning facts about a possible crime. He would have been derelict in his duty if he did not pursue this matter.
It's also worth reminding people that Fitzgerald didn't create this case out of whole cloth for his resumé. It was underway and the Bush DOJ appointed him to the case. Now that he has finished his work and there is an Administration scalp on the wall, expect Fitzgerald to join the ranks of the recently "retired" U.S. Attorneys. The fact that Fitzgerald performed upheld his oath to the Constitution and the Law and pursued the case vigorously goes along way to explaining why Bush wants U.S. Attys in office who swear an oath to him.
As to the argument that "there was no crime..." only perjury. First, perjury is a crime. And so is Obstruction. Second, because of the perjury and the cover-up any crime cannot be determined. If Libby and Cheney committed no crimes, why cover it up and lie under oath? We'll never know, because they decided having one of them go to prison for lying about it was preferable to telling the truth.
UPDATE: More at TAPPED and from Mark Kleiman