In 2008, both target-date ETFs and target-date mutual funds took a huge blow as the markets slid downward. Target date funds that were more aggressively allocated for further retirement dates were hit worst. TDV fell 40% in 2008. While the retirement date for its target audience is still far off, these returns are unnerving. Funds like TZD are dangerous because they combine a long-term trading strategy with a product that trades daily on an exchange. It would be difficult to watch an ETF fall 40% and stay invested for the long term. Investors who have any level of financial knowledge are better off building a basic, diversified portfolio rather then putting all their eggs in TDV's basket. 8.Claymore/BNY Mellon Frontier Markets ( FRN). The risks of investing in this "frontier markets" ETF are not yet worth the potential rewards. FRN invests in the most emerging of emerging markets, areas that are inherently volatile economically and politically. FRN's top five country allocations are Chile, Poland, Egypt, Colombia and Kazakhstan. The three-month average daily trading volume for FRN is a low 13,221. Since the fund is illiquid, investors face illiquidity compounded with inherent volatility. While this fund may be worth a look in the future, for now it is simply dangerous. 7. UltraShort Health Care ProShares ( RXD). RXD has two things going against it: the fact that it's illiquid and the fact that it's leveraged. ProShares, the pioneer of the leveraged fund industry, released RXD as part of a short/long pair in a series of leveraged sector funds.