Once upon a time, Art Chicago was a high-rolling event, the jewel of the international fair calendar. Well, the invisible hand of the market giveth, and it taketh away. Art Chicago is no longer, strictly speaking, an art world event. In some last-minute scrambling, after what seems to have been a serious monetary shortfall that threatened to scuttle the entire event, Art Chicago organizer Thomas Blackman sold the fair to Chicago’s Merchandise Mart. It’s the end of an era.