To add a bit of seriousness to this question, just think about these things:
1) The brain likes to link things up. For example, many times I'll have some random thought one day about some old kids' TV show that hasn't been shown or talked about since the early 90s. And then amazingly a week later, there'll be some documentry or something about that very show, that I knew nothing about! Now, imagine if that documentry hadn't been on. My random thought would have been just that: some random thought, one of many I have. It didn't really mean anything. But because, in some unrelated incident, it gets talked about on TV, that makes my brain think back to the thought I had, and thus I had what some call a preminition.
2) Secondly, as rojash and bednobs are suggesting, the statistics are way against you. I wonder how many random thoughts you've had that have turned out not to have happened, as rojash asks. This links back to my first point. Because they didn't happen, you forget about them and that's that.
And even if you go so far as to believe that the two thoughts you've had that have come true are indeed mystical preminitions of some sort, they aren't too hard to imagine anyway. I mean, for a few years before Diana died, there was not only controversy over her and Dodi's affair, but I also remember her going into a few war-torn places campaigning against landmines. Her death really isn't that unreasonable statistically, if you look at the situtation around her at that time.
Another example would be my preimition a few weeks ago that Steve Irwin would die (I'm making this up). It's really not too unlikely when you remember the stunts that he pulled around crocodiles and poisonous snakes, expert or no expert.