Somewhat ironic that this memo got leaked but I think in this case it actually serves their purpose for it to be read by everyone (including potential employees). I think this part is key and is something I've always wondered about: >While it may seem flattering to be approached, it’s important to remember that you’re getting played. The success of these outsiders is measured by obtaining Apple’s secrets from you and…
There's four reasons people leak information:
1. Out of moral responsibility to report unsafe or illegal activity.
2. To cause direct harm to the root organization because they feel slighted by some action in the past.
3. The "leak" is officially sanctioned as part of a submarine.
4. Ego.
Numbers 3 and 4 are the biggies.