O.J. Simpson was heckled mercilessly before he was escorted out of the National Sports Collectors Convention in Rosemont, Ill., on Saturday. Darryl Rivera, who captured some of the booing with his video camera, tells us, "People were yelling, 'Killer!' Another guy yelled out, 'Guilty!' " Simpson, who was asked to leave because he hadn't gotten prior approval from organizers to sign autographs, was hawking 8- by 10-inch photos of himself for $100 a pop — cash only. Rivera said Simpson was traveling with several "good-looking blond women."