There is a very real possibility of compromising that intelligence source. If that source is compromised, it becomes useless (in the event the source is technology (SIGINT)), or terminated (in the event it is a person/people (HUMINT)).

My problem with this logic is that this is the exact reasoning given for why the Bush administration couldn't give the public more evidence before the invastion. Now that Iraq is our sand box to play in, we can go and "discover" any evidence we already know exists. The Bush administration would love to justify the whole thing with a canister of nerve gas or two, but they can't come up with any.

Matthew