My best friend Michaela and I didn't realize we were best friends until junior year when I rowed from Tangier to Spain to visit her, and save her from all the unkosher pig meat and predatory men that followed her everywhere. I told her that only a true friend would brave international waters without a visa. And she said, "I wish you had told me you were planning on visiting me because I already had plans this weekend." But then she got over it, because that's what best friends do, and we had so much fun.
Conversely, my old landlord and I got along splendidly at first. We didn't realize we were enemies until she knocked down a whole wall in my bathroom without telling me when I was at work.
The point being, sometimes it takes time to determine who is really a friend and who is an enemy. People reveal their true colors when they're truly tested. People can shape-shift like chameleons, or mutants or Romneys. Or even when they're not running for president, people can surprise you and deceive you.
It can be confusing out there for well-meaning young people who still expect only the best from others. Drawing on my limited life experience, I've separated people and things into two groups: those who you can trust with your friendship and those who you must swear on your first born to destroy. And then I made this slide show. Enjoy!