Something deeper and more illegal than we have imagined

Possibly took place with the warrantless wiretapping. Eavesdropping on senators' phone calls so they could be blackmailed? Sabotaging presidential candidates? Listening in on other countries diplomatic efforts?

Josh Marshall says it must be bad: (my bold)

Of course, 'data mining' can mean virtually anything. What kind of data and whose you're looking at makes all the difference in the world. Suggestively, the Times article includes this cryptic passage: "Some of the officials said the 2004 dispute involved other issues in addition to the data mining, but would not provide details. They would not say whether the differences were over how the databases were searched or how the resulting information was used."

To put this into perspective, remember that the White House has been willing to go to the public and make a positive argument for certain surveillance procedures (notably evasion of the FISA Court strictures) which appear to be illegal on their face. This must be much more serious and apparently something all but the most ravenous Bush authoritarians would never accept. It is supposedly no longer even happening and hasn't been for a few years. So disclosing it could not jeopardize a program. The only reason that suggests itself is that the political and legal consequences of disclosure are too grave to allow.