(Bloomberg Businessweek) — In September, dozens of financial advisers from around the US converged on an upscale Greek restaurant in Midtown Manhattan for cocktails and dinner. The venue, Avra Madison Estiatorio, gets rave reviews for its first-class service and grilled branzino, but the main attraction that evening was tennis legend John McEnroe. The following day, after presentations on alternatives to stocks and bonds, the crowd …