Grassley gives Holder a note:

A strongly-worded letter from Republican oversight members of Congress to Attorney General Eric Holder today came with an unusual handwritten notation at the bottom. Penned in blue ink by his signature, Sen. Charles Grassley's (R-Iowa) writes: "PS: You should check to see if you are getting accurate information from your staff. You might be ill-served."
And Sipsey Street had about the same thought I did when I read this, though he goes into much more detail:
"You may be ill-served" What a hoot! This is Grassley's tongue-in-cheek invitation to throw Melson and Breuer under the bus, and that's when the serious truth leakage begins because they'll use the Nuremberg defense, "I was only following orders." And they will have proof of it.

Grassley, knowing everything that he knows from the whistleblowers and leaked documents, has a very good idea of how involved Holder is in all of this -- up to his eyeballs. Worse, Holder knows that he knows. I'd be surprised that if, when he saw the postscript, Holder didn't ball the letter up and throw it across the room with a string of curses.

The only thing that can possibly, maybe, save Holder now is for the Gunwalker men, Melson and Breuer, to go happily skipping hand-in-hand like little kids down the path in Fort Marcy Park to their own perdition, following the Sicilian prescript that "Three men can keep a secret if two of them are dead."

Holder is toast and this is Grassley's way of reminding him of it. What he is really saying is, "Sooner or later we will have your subordinates under oath. Got a fall-back plan for THAT?"
I just thought "He's giving Holder an out, isn't he? A way to try to blame it on subordinates?" Then I thought "But what happens when the subordinates disagree?"