Condé Nast’s once-ballyhooed Portfolio magazine will cease publishing immediately, staffers were told this morning. “The five main categories of advertising a publication like ours depends on are really in trouble,” Condé Nast’s group president told the New York Times. The magazine launched in April 2007, and has witnessed a historic 60.9% plunge in ad sales over its short existence. (More Conde Nast stories.)