From my experience in London I'd say a major factor is the financial sector pulls in lots of ambitious talented developers and pays them well enough that they c

From my experience in London I'd say a major factor is the financial sector pulls in lots of ambitious talented developers and pays them well enough that they can easily afford to take time-off to work on their own thing. In London at any startup event you go to in London I'd say around ~20-30% of the founders have backgrounds in the financial sector. I think investment banks are more nurturing of that sort of behaviour than many other firms, they're willing to let people go off and experiment and then rehire them back if stuff doesn't work out for them. I left the bank I was working for, and they became my first client (on a consultancy basis) to help finance my startup and after the consultancy contract was over they gave me an open invite to call them if I ever wanted to come back. I know many other people who have similar stories.