No they aren’t. A “public figure” such as a politician is not the same as a celebrity who likeness is their income.
You can use “public figures” likenesses, not celebrities.
However McCain simply compared Obama’s celebrity status to that of Paris & Britney in a political ad, so I think they’ll lose that case.
I’d say safely that Hilton and Britney are public figures. I don’t see People’s magazine or ET or the other outlets getting sued for posting their photos. In fact the Paparazzi do pretty well.