The most profitable way to steal must be conning old people.
Hmm, not even close. The most profitable way to steal is to be the CEO of a multi-national bank. You can steal as much as you want, and you never get caught. See, Jamie Dimon (JP Morgan Chase), LLoyd Blankfein (Goldman Sachs), Vikram Pandit (Citicorp), Richard S. Fuld (Lehman Brothers), Bob Diamond (Barclays), et al.