Missing concept #2: Trust boundary

[adamshostack]

The second concept I'll advocate is trust boundaries. They are also a tremendously important part of "most important areas of concern that software developers must be aware of. "

Suggested core text: "Know what code is trusted to make security decisions, and why that code is resistant to attack by an attacker with a debugger or a proxy."

[andreashappe]

maybe discuss this in the context of #32