Let's say someone in their mutual fund holds only the SPY's so they track the market, why would they not just buy the SSO? Assuming the market always EVENTUALLY makes new high's, it seems to me that you're getting great leverage on your money and while the swings will be more volatile, the end result will be double the eventual gain that the market incurs. It's not like you're leveraged up to one stock.. it's the whole market.. I must be missing something because it makes no sense to me to hold the SPY's over the SSO assuming you are a long term, buy and hold IRA investor type.