Why do some people remember dreams and other don't?

It's a question that I ask myself often. It's very rare that I don't remember my dream, and my dreams are often very vivid and quite often strange (I once had to save the world from blue lamps which wished for world domination... yes lamps as in the kind that give light...). In fact, I often enjoy my dreams so much that I will force myself to sleep more so that I can find out what happens in the end (rather like a film). I also sometimes have a hard time deciphering what was a dream and what wasn't, and many of my childhood memories are of dreams that I had.

But then my boyfriend very rarely remembers his dreams, and when he does they are often quite normal (as dreams go). And he certainly doesn't remember them for very long.

So what I'm asking is, why do some people remember dreams and other not - And why are some peoples dreams tripper than others?