ATRIOS WRITES: "Unlike Ann Coulter, I'm no constitutional scholar, but I have been a wee bit puzzled why the prohibition on ex post facto laws would't prevent this telecom immunity bullshit."
The answer is that only criminal, not civil, action is prohibited under the ex post facto prohibition. (Don't feel bad, Atrios -- James Madison himself was confused on this at one point and was corrected, if I recall correctly, by James Iredell at the constitutional convention). In addition, ex post facto is about penalties, not amnesties. Congress is not prohibited from blocking civil actions by statute, particularly where there's a national security angle. This goes back at least to Dames & Moore v. Regan, which involved the Iranian hostage settlement, and really dates back to cases in the 1930s dealing with claims against the Bolshevik government in Russia on behalf of Tsarist-era creditors, etc. One might regard this as giving the President too much power over domestic legal actions as part of "foreign affairs" activity -- I regard it that way, actually* -- but it doesn't represent any sort of new departure.
* To my mind, a statute barring a previously valid legal claim that has actually been filed comes close to a taking, as well, but that goes beyond the scope of this post.
UPDATE: A related item. I wouldn't call $25,000 "newly flush with cash" -- especially for a Rockefeller -- but the graphic is suggestive.