It is possible for the reverse of contango to happen (called backwardian) where the etf would actually go up in the short term while the commodity stays flat.
Ultimately though, the reason why contango has to win in the long run is that there is a real cost associated with holding oil. Contango should be a lot cheaper with gold, since it's cheaper to store gold.
The amount you might lose to contango in an ETF is probably a lot cheaper than if you tried to horde a bunch of oil in a tank on your property anyway, so it's not really a terrible investment.
Moral of the story: don't invest in instruments you don't understand.
Ultimately though, the reason why contango has to win in the long run is that there is a real cost associated with holding oil. Contango should be a lot cheaper with gold, since it's cheaper to store gold.
The amount you might lose to contango in an ETF is probably a lot cheaper than if you tried to horde a bunch of oil in a tank on your property anyway, so it's not really a terrible investment.
Moral of the story: don't invest in instruments you don't understand.