And a furor erupts in academic and [not necessarily entirely overlapping] plaintiff-oriented circles:

• Michael Dorf, FindLaw;
• Howard Wasserman in a series of critical posts at Prawfsblawg: first, second, third (implications for Bivens and "supervisory liability" claims), fourth.
• Tony Mauro, NLJ; ABA Journal (Souter dissent: to overcome motion to dismiss, allegations "need not be plausible" and anything short of rants about "little green men" should do it);
• Richard Bales, Workplace Law Prof;
• Scott Dodson, Civil Procedure Prof;
• Alexandra Lahaf, Mass Tort Litigation;
• Andrew Longstreth, American Lawyer (decision could affect securities litigation, in particular cutting down on "fraud-by-hindsight" actions);
• WSJ Law Blog (quoting some reactions from the defense side: some had imagined Twombly would be restricted to antitrust claims, but the Court clearly means to apply it across the board; bare "notice pleading", in which the only requirement of pleadings is that they place a defendant on notice of the nature of the dispute, now a thing of the past in federal courts).

To declare my own sympathies: in my first book, The Litigation Explosion (1991), I argued at length that the system of notice pleading, in which the barest and least informative allegations are enough to get into court, is high on the list of factors contributing to our national oversupply of litigation. That doesn't necessarily imply that any one way of fixing things, or of narrowing or winnowing out lawsuits at the pleadings stage, is the right way; interestingly, no less a figure than Richard Epstein has written a SSRN paper somewhat critical of the high court's Twombly decision, of which Iqbal is an extension. But it does mean I tend toward impatience with the notion that everything was fine in the Conley v. Gibson era, and that if opponents who have done nothing wrong happen to be ruined by the cost of responding to vague, conclusory and shifting allegations, well, you can't make an omelet without breaking eggs etc.