They wanted to get Plame...but now, in effect, they've outted everyone who's EVER used that company as a cover (put anyone who's innocent and worked there in the line of fire).
What's funny about this - is given the timing (Libby just got approval to get those classified documents), I think someone (not in Libby's camp) leaked this to the press. The (cough) smart foreign-intelligence officers have already looked at this info when it first came out.
I wonder how much intelligence has been compromised and how many other agents we've lost.