For the heirs of some uber-weathy clans, trading on the family name comes easy. It certainly seemed a natural fit for David B. Guggenheim, who began to appear on the dealmaking scene back in the 1970s, using his name to woo investors.

One problem: David Guggenheim was actually David Birnbaum, of Ditmas Park, Brooklyn. And not surprisingly, the real Guggenheim family, which launched a fledgling investment firm in 2000, wasn't so keen on Birnbaum's activities.