Beware of Short term ETF trap

I always suspect ETF like USO is for short term investors, I.e., traders but cannot figure out exactly why. Then I came across this article and it explained the issue in a details.

http://seekingalpha.com/article/123577-is-the-uso-etf-a-piece-of-junk

This probably applies to other commodities ETF as well since normally the fund would not hold the real stuff in inventory, unlike the GLD, which means those ETFs would have to use future instruments as their trading strategy which suffers the same contango as USO does.  Even though not exactly the same for comparing purpose, but you could get a good idea how a short term focused ETF would perform by looking at uyg (short term) and xlf (ling yerm) at 5 year horizon.

I hope SEC could force ETF vendors to make this short term/long term distinction more clear.

Not all index based ETF are pass investments. Buyers warned.