The amount of freedom he or she has in choosing to engage in the controversy in the first place (e.g., if they were forced into the public light). See Wolston v. Reader's Digest Association, 443 U.S. 157 (1979).
Whether he has taken advantage of the media to advocate his cause. See Time, Inc. v. Firestone, 424 U.S. 448 (U.S. 1976).
Keeping in mind the difficulty of making the determination of who is a limited-purpose public figure, we've collected the following cases which might be helpful. Courts have found the following individuals to be limited-purpose public figures:
A retired general who advocated on national security issues. See Secord v. Cockburn, 747 F.Supp. 779 (1990).
A scientist who was prominent and outspoken in his opposition to nuclear tests. See Pauling v. Globe-Democrat Publishing Co., 362 F.2d 188 (1966).
A nationally-known college football coach accused of fixing a football game. See Curtis Publishing Co. v. Butts, 388 U.S. 130 (1967).
A professional belly dancer for a matter related to her performance. See James v. Gannet Co., 40 N.Y.2d 415 (1976).
A Playboy Playmate for purpose of a parody. See Vitale v. National Lampoon, Inc., 449 F. Supp 442 (1978).
Courts have found the following individuals not to be limited-purpose public figures (and therefore private figures):
A well-known lawyer and civic leader engaged in a very public trial involving police brutality. See Gertz v. Robert Welch Inc., 418 U.S. 323 (1972).
A socialite going through a divorce who both collected press clippings on herself and held press conferences regarding the divorce. See Time, Inc. v. Firestone, 424 U.S. 448 (U.S. 1976).
A Penthouse Pet for purposes of parody. See Pring v. Penthouse Int'l Ltd., 695 F.2d 438 (1982).