Here's a link to the Register's editorial on the House Judiciary Committee's decision to issue contempt citations to White House chief of staff Josh Bolten and former White House counsel Harriet Miers. Several points are worth noting. First is that the words "executive privilege" appear nowhere in the Constitution, though many president's have claimed it. Second is that the law is far from settled. The Supreme Court's U.S. v. Nixon decision recognized the claim could be valid to make sure a president got candid advice, but the privilege wasn't absolute, and it forced Nixon to turn over tapes to the special prosecutor anyway. He did so two weeks later and four days after that resigned.
The other is that it's ridiculously partisan. Democrats thought Clinton was protecting the institution when he invoked executive privilege, while Republicans thought he was abusing power. Now the tables are turned (the Judiciary Committee vote was along party lines).
The comments of Bruce Fein, Reagan Justice Dept. official and head of the American Freedom Agenda organization, here, and here, are worth some respect. He says even the "candid advice" argument is a little phony; there's always an exception for criminal investigations and every presidenial aide knows there's a strong likelihood of leaks, but in his experience they're candid anyway; they would have to be, at least to the extent that the president himself can handle candor.