Elon Musk's SpaceX has been accused of acting like the 'universe's biggest Ponzi scheme' after Nasdaq-100 inclusion pushed its shares into millions of retirement-linked funds, even as the stock slipped from its early highs this week. The charge, centres on the risk that ordinary investors were pulled into SpaceX exposure without knowingly choosing it, a point that has set off a sharp debate over index rules and passive investing. SpaceX And The …