SpaceX offers a great test for whether passive index-tracking funds are distorting the stock market, with the rockets-to-tweets company's entry to the Nasdaq-100 index today forcing the massive QQQ ETF to buy its shares.

The provisional result is disappointing for investors who thought automatic index buying would boost SpaceX shares. Despite being added to the FTSE Russell, CRSP and MSCI indexes collectively tracked by hundreds of billions of dollars, SpaceX's price at yesterday's close was a few cents below the close on its first day of trading.

Those who bought at $135 a share in the IPO and held on are still up about 19%, but they made all their money on day one. For more on why index entry isn't the boon to SpaceX performance many hoped, see my Streetwise column from a few weeks ago.