It depends on the nature of the dreams. If the general environment or feel of the dream is hostile it can mean that you feel the person is untrustworthy or dishonest, however if they appear as a friend or ally in the dream it can mean the opposite. Or it could just mean you have or been spending too much time with that person, as Freud said, sometimes a cigar is just a cigar. That said I find that if the dream leaves you wondering what it means, then it usually means something.
Dreams don't necessarily mean anything. They are just a way for your subconscious to express thoughts. Therefore, you're more than likely thinking about this guy a lot, either consciously or unconsciously, so he appears in your dreams since he's on your mind.