Both ASO and GRN command very little trading volume, but investors should not expect to see GRN disappearing anytime soon. The iPath line of ETNs spawned from the same family as the highly popular iShares line. iShares has long been home to popular products such as iShares S&P 500 Index ( IVV) and iShares Russell Midcap Index ( IWR), which pay for themselves and their less-successful peers. While the closing of ETFs may be a pain for shareholders, the Darwinian result has helped take poor performing products off the market. Upstart ETF issuers have to be lean and mean, delivering products that customers want and taking aim at ETF standards offered by other fund groups. The industry is experiencing a fundamental shift, however, highlighted by the recent BlackRock ( BLK) acquisition of iShares. The players at the top of the ETF industry are getting bigger and asset managers like Schwab ( SCHW) will soon be offering their own line of products. Here's to hoping that consumers will continue to demand excellence and that the viability of funds will keep the ETF universe from becoming bloated.