I think everyone has had an experience with deja vu; I know I have and it's really freaky when it happens. I'll be standing there talking to someone and that feeling comes over me that I've done this before; I've had the exact same conversation with this person and I can even predict what they're going to say.
With someone I know, that's one thing; having this experience with someone I've never met before is really bizarre.
I've heard all kinds of theorys as to what deja vu is: a "delay" in the brain, reincarnation, someone in the future has changed the past and we sometimes 'repeat' things, it's all in your head, it's Satan.........
I'd be interested to hear what sort of experiences you've had with deja vu and what you think it is.......