EVERY other Sunday afternoon since April 2003, advocates of animal rights have gathered with bullhorns across from 279 Central Park West, near 88th Street. They are there to protest Huntingdon Life Sciences, a product-development company that does scientific tests on animals, and its chief executive, Andrew Baker, who lives in the building. Or does he? Months ago, residents heard that he had moved out. And so, they wonder, why don't the protesters stop? "Someone would first of all have to provide really good proof that he's not in the building," said Camille Hankins, who organizes the events for the group,...