May a defendant file a new forum non conveniens motion each time a plaintiff files an amended complaint? That was one of the issues decided in Ellis v. AAR Parts Trading, Inc., 1-02-3744 and 1-03-1156 Cons. (1st Dist. 2/4/05).
And here's the answer: "[A] new challenge to forum is appropriate when new matter[s], new parties, or new causes of action or theories are brought forth in an amended complaint." For a detailed analysis, see the opinion.