As Rex Harper, the bottom-feeding celebrity shutterbug of Paparazzi, Tom Sizemore, an actor with sleaze in his marrow, does a variation on his specialty: the lowlife operator who grins just at the moment he's sliming you, as if he were asking you to share in the delight of his corruption. Harper sets about snapping invasive family photographs of a newly minted schlock action star named Bo Laramie, played by Cole Hauser with an overcooked glare of bug-eyed outrage that renders him even steelier than Peter Weller. In its early scenes, ''Paparazzi'' exploits, with a certain brute B-movie effectiveness, an ugly reality -- that even the worst excesses of tabloid photographers are part of a tacit contract with the public. The long-lensed rats do the digging, and we glory in the dirt. That's a tasty subject for a movie, but once Rex and his fellow stalkerazzi cause Bo and his family to get into a car accident that echoes the one that killed Princess Diana, it doesn't take long for the film to devolve into a ludicrously far-fetched Celebrity Death Wish.