There was an interesting post on Ron Miller's blog, The Maryland Injury Lawer Blog, on the recent case of Robertson v. Iuliano, No. 10-1319 (D. Md. Feb. 4, 2011). Robertson v. Iuliano illustrates that in a case filed in state court, where diversity jurisdiction would exist but for the presence of forum defendants, and the forum defendants have not yet been served, the non-forum defendant can, in many jurisdictions including Maryland, still remove the action to federal court.
In fact, in the Robertson case, the non-forum defendant removed the case to federal court before he or any of the other defendants were served.
Under the unanimity rule reaffirmed by the 4th Circuit in its recent en banc opinion, where there are multiple defendants, it is necessary for the other defendants in the case to consent to the removal within 30 days of their being served. Here they apparently did, because they filed oppositions to the motion to remand. The District Court denied the plaintiff's motion to remand.
In a medical malpractice case, removal would result in the application of the more stringent Daubert standard for the admissibility of expert testimony, which would be reason enough to do it.
I can understand why this result could be viewed by the plaintiffs' bar as unfair, but on the other hand, I've seen many cases where a forum defendant was joined in a complaint for no apparent reason other than to destroy diversity.
There was a recent article on this topic in DRI's journal, For the Defense, in April, 2010, which among other things provided citations to other jurisdictions where this is the rule. See Tiffany Reece Clark, Removal Before the Forum Defendant Is Served - The Plain Language of 28 U.S.C. sec. 1441(b). Here are some other perpectives on this issue, one from the defense side, one from the plaintiffs' side, and one giving more extensive background on pre-service removal.
In sum, in the Robertson case the defense used a combination of two rare procedures -- removal before service of the forum defendants, and removal even before service on the client -- to steal a march on the plaintiff and gain a tactical advantage that may turn out to be decisive.