FISA/Wiretap Flap

Kevin @ Political Animal brings up a point I didn't know and then asks the obvious question.

And there's more: it wasn't even a matter of keeping the NSA program a secret from the FISA court. The judge knew all about it, and even warned the administration not to use information from the unapproved program as the basis for further wiretap requests.

So what's the deal? It must be pretty obvious to everyone that there's more going on here than the administration is fessing up to. Since there was no apparent reason to bypass the law, there must be an unapparent one. But what?