A CNN.com article from 2000 about cert denials included this note:

[The Supreme Court s]aid no to G. Gordon Liddy, who failed in his bid to fend off a defamation lawsuit by a woman he linked to an alleged call-girl ring at the Democratic National Committee at the time of the 1972 Watergate break-in.
The court, without comment, rejected an appeal in which Liddy argued that the woman should be considered a public figure who would have to prove "actual malice" to win her lawsuit.

For those of you know Liddy only as a radio blowhard, he served four years in prison for arranging the Watergate burglary of the Democratic Party headquarters. I don't know the facts of this defamation case, but I wondered: If it was the defamation itself that made someone famous, would the defendant be able to use the "public figure" defense? For example, Monica Lewinsky was a nonentity until she was alleged to have had sexual relations with President Clinton. If those allegations had been untrue, but she did not bring suit until her name and face had been in every newspaper in the world, would she still be considered a "public figure" for the purposes of defamation?

(Of course, the whole query collapses if the only public figures are people who became famous for good reasons, as this definition implies, which means that people like Lewinsky still maintain the "private figure" standard.)