"Complementary activities"

It's bad enough that banks are allowed to also be brokerage firms but once you allow them to also hold interest in concerns "complementary to a financial activity" you soon figure out that this includes.. well... pretty much everything.

And so you get stuff like this.

But banks aren't just buying stuff, they're buying whole industrial processes. They're buying oil that's still in the ground, the tankers that move it across the sea, the refineries that turn it into fuel, and the pipelines that bring it to your home. Then, just for kicks, they're also betting on the timing and efficiency of these same industrial processes in the financial markets – buying and selling oil stocks on the stock exchange, oil futures on the futures market, swaps on the swaps market, etc.

Allowing one company to control the supply of crucial physical commodities, and also trade in the financial products that might be related to those markets, is an open invitation to commit mass manipulation. It's something akin to letting casino owners who take book on NFL games during the week also coach all the teams on Sundays.

Seems legit.

Adding: We could have asked, "What could possibly go wrong?" But we already know the answer is, if anything goes wrong, the banks are all re-capitalized for free courtesy of the taxpayers.  So, you know, hooray for the free market.