As ETFs have transitioned from a closet industry to a mainstream investment vehicle, a growing number of investors has become familiar with the exchange-traded structure and the nuances of of the industry. Most advisors now recognize the “super tickers”–SPY, GLD, EEM, etc.–and have a good feel for the size and scope of the industry. But [...] Related Stories: Seven Surprising ETF Trading Stats January ETF Data: Industry Springs A Leak Five Facts About HOLDRS Every ETF Investor Must Know