Why is it that I can't trust anyone?

As you have no doubt learned by reading my previous posts, [At this point in the story, our writer looks away from the computer screen. While his head is turned, if you have not read all 3 of his previous posts, you should do so. You can do it quickly and he will never know.] I have had some personal bombshells dropped into my life in the past 3 years. I have dealt with these problems in a very human and fairly dignified manor. I have cried, screamed, run screaming, thrown things at walls, run with sharp scissors, rended my shirt, thrown a temper tantrum and I threw all my toys into the front yard. So, I dealt with it the best I could. I am much better now. I don't ever rend cloth, anymore. Anyway...
Why is trust so elusive? Why is it that I can't trust anyone? Why does it seem like there are so many more dishonest people in the world today? (And don't worry, this is not another "Honesty Blog") I have met so many different people in the past three years. People, that I know, I would never have met in my former life. But, why is it that I can't trust any of them?
I keep getting taught this same lesson over and over again. [Don't Trust Anyone!] I have had numerous occasions to trust new people I have been introduced to and almost 90% of the time, they are just another chapter in the lesson.
See, I give everyone 100% trust the moment I meet them for the first time. I don't know why, it was the way I was raised or something I ate earlier. Anyway, I do that for everyone. I give them trust, they steal stuff from me. In some weird little corner of the universe, this balances out. (I think, I am just guessing. I can't bring myself to consider the alternative that I am just very naive. Nah.) So, I trust them, they take what they want and we part ways. I go away with more trust homework and they get movies, music, money, credit cards, whatever they find laying the house. Maybe, just maybe, I will eventually learn that tough lesson, but the world will be a little colder place when I graduate.