The exchange traded fund (ETF) industry is currently brimming with excitement over a couple of new all-world funds.

But can keeping it too simple be a wise strategy? Gary Gordon for ETF Expert doesn’t think so.

An obvious pro to an all-world fund is simplicity of it all. Plus, there are fewer fees and fewer numbers to keep track of. This way you avoid higher fees and the increasing complexity of too many ETFs. Plus, with ETFs you get total flexibility and transparency.

On the flip side, there is the fact that just one ETF is not great for a buy-and-hold investor. Portfolios have to be more dynamic than what one fund can offer and equity investors should not stay handcuffed to one type of index.

Penelope Wang for Money Magazine points out that some of the newer and more narrowly focused ETFs may not be actually investing in an index, but using a strategy.  While ETFs are made to track an index, providers may have to optimize the ETF when, for any number of reasons, replication is not possible.