Ted Frank at Point of Law was early to recognize the import of the May 21, 2007 decision in Bell Atlantic v. Twombly, 127 S.Ct. 1955 (2007). A longer look at the decision was taken in Dodson, Pleading Standards After Bell Atlantic Corp. v. Twombly, 93 Va. L. Rev. In Brief 121 (July 9, 2007), which gives a thorough overview and will convince you that it is worth your while to read the decision. (Thanks to the SW Virginia Law Blog for the link to the Dodson article.)
It does now appear that the decision will have a major effect on notice pleading rules. As of today, the decision had already been cited around 470 times. Its effect is not going to be limited to antitrust cases. Essentially, where the previous standard was that "a complaint should not be dismissed for failure to state a claim unless it appears beyond doubt that the plaintiff can prove no set of facts in support of his claim which would entitle him to relief", under Twombly a complaint must present enough facts to state a claim that is plausible on its face.
Defense counsel are going to have to rethink the cost benefit analysis of when it makes sense to file Rule 12(b)(6) motions. There is more of a chance of success now in light of Twombly. In particular, fraud claims and conspiracy claims that are pled without sufficient supporting facts should be candidates for a Twombly motion. Also claims for punitive damages that are not supported by plausible factual allegations should be attacked at the outset of the litigation with a Twombly motion.
Surprisingly, the first decision from the D.C. Court of Appeals to cite Twombly did so in the context of a motion to strike affirmative defenses and counterclaims under Rule 12(f). See Franco v. National Capital Revitalization Corp., No. 06-CV-645 (July 12, 2007). As that opinion suggests, Twombly may also require changes in the way that affirmative defenses, counterclaims, and cross-claims are pled.