Investors of the world unite! You have nothing to lose but your chains to poor performance! That’s one way to interpret the somewhat radical May Day upheaval at AllianceBernstein. The U.S. investment-management firm once renowned for its stock-and-bond-picking skills ousted Chairman and Chief Executive Peter Kraus in a move that suggests steady decline is no longer acceptable in a market dominated by indexers, exchange-traded funds and other lighter-touch strategies. His tenure was bookended by crisis. The firm controlled by French insurer AXA tapped Kraus, a former co-head of asset management at Goldman Sachs, to replace veteran Lewis Sanders in December