Thought waves attract objects toward which they are oriented. It might be that you're more "magnetic" than most people.
Then again, a good deal of it may just be mere coincidence that you've associated with previous events of similar nature -- just saying. The reason horoscopes are proscribed to by so many people is because they are terribly vague. "You will meet a tall, dark, and handsome stranger" is a very subjective description. Are these people you meet of exact likeness to the ones in your dream, or of similar personalities? If you're dreaming about something, your mind could be on it, and you are more likely to notice things that are relevant to your interests while dismissing the rest as "background noise", so to speak. You meet people of all different personality types every day, one will probably stand out if you've dreamed about them.