What was your game-plan if you'd stumbled upon something highly personal and sensitive in their mailboxes? Or if one of their friends had sent them a person IM while you were logged in as them? The fact is, you could have easily approached these people face-to-face, offered to show them the risks they were exposing themselves to using your laptop, and give them the choice as to whether you took control of their accounts. While it appears that you did what you did with the best of intentions, you violated the privacy of the people whose accounts you accessed; broke a variety of laws; then documented your crime in your personal blog.
You describe your targets as lacking judgment. Maybe you should consider your own.
You describe your targets as lacking judgment. Maybe you should consider your own.