From the start, avoid any ETFs below a $100 million market cap. Anything smaller puts you at risk of inadequate liquidity, too large a bid/ask spread and tracking error. Even $100 million can be too low. The bigger the market cap the less trading risk. There are plenty of free services that allow you to screen out the smaller ETFs and minimize your trading risk. The focus of this article, however, is investing risk or the relative investment potential of the ETF.