Not All ETFs Are As Simple As You ThinkTom Lydonupdated Jan 09, 2010TweetAt GET.com we maintain complete editorial integrity on our content & provide transparent & unbiased information. Companies don't pay us to include their products although we receive a compensation when you successfully apply to products from our partners. See how we make money here.At GET.com we maintain complete editorial integrity.As the world of exchange traded funds (ETFs) expands, more products become available, but not all of them are as simple as you'd think. ETFs are becoming more sophisticated and complex, and every investor needs to know how they work for more efficient investing.Every investor needs to study up on ETFs before actually investing in them, remarks John Spence for MarketWatch. This research is crucial step that many investors have ignored, burning them in the process.For instance, United States Natural Gas (UNG) dropped more than 50% last year, but investors still put money into the fund in an attempt to time a bottom to natural gas prices. According to Morningstar, investors may have lost $1.5 billion betting on the ETF. Additionally, the ETF lost money rolling futures as a result of "contango," and the fund also has a tax structure like a limited partnership.Nicholas Colas, ConvergEx Group chief market strategists, stresses the need to look at an ETF's "portfolio construction, re-weightings, management fees or index being tracked." Different ETFs have varying sector weightings - some ETFs that track similar things may even have sector weightings that are completely disparate. Furthermore, some ETFs have high weightings in their top holdings, so be sure to look at what makes up the fund and be sure you are comfortable with it.Editorial Disclosure: Any personal views and opinions expressed by the author in this article are the author's own and do not necessarily reflect the viewpoint of GET.com. The editorial content on this page is not provided by any of the companies mentioned, and has not been reviewed, approved or otherwise endorsed by any of these entities. Opinions expressed here are author's alone, not those of the companies mentioned, and have not been reviewed, approved or otherwise endorsed by any of these entities.