Thirty times leverage means that if you lose 3.3%, you wipe out all your capital.
In the first few years of the G.W. Bush administration, the banking authorities decided it would be OK to allow five banks to increase their leverage from 12:1 up to 30:1. Which five banks, you ask? Bear Stearns, Lehman, Merrill Lynch, JPMorgan, and Goldman Sachs.
How did that work out, just five years later? Three are gone and two survived with large dollops of taxpayer money.
Is it really any surprise that Goldman and JPMorgan are making record profits on the underwriting and trading side of the business? Hell, if I could eliminate 50% of my competition, my profits would grow too!