This place needs more skeptics right now.
DEVIL'S ADVOCATE POWERS, ACTIVATE!!Potential causes:
1. Drug/Booze induced dazes:
"Man, I totally remember going to the bathroom!" "No, Rojo, you went to the
KITCHEN and took a whiz in the trash can." "Oh."
2. Complete fabrication.
Friends or no, this happens WAY more than you'd like
or know. I don't want to hear that your friend is a saint either. I had a girlfriend that was a 'saint'. You don't want the know the depraved acts she would commit... in a completely innocuous situation.

3. Strong prior stimuli or consistent stimuli between parties while asleep.
Such as multiple people being asleep in the same area with a TV on, especially if said movie or show that is playing is already very familiar to the subjects, multiple people may dream they are somehow connected with the show or the subject of it.
4. Simple semi-conscious sleepwalking.
Lucidity and
actual evidence of being outside point directly to this.
*Have an unrelated 3rd party interview each person individually immediately after a dream 'session' asking specific, pointed questions, not allowing the 'dreamers' to ramble about the experience. If any stories match, then you
might be able to
entertain the thought that it
could be a possibility, even though it would still be entirely probable that they're faking every bit of it, or at best case, that any similarities discerned were a direct result of previously mentioned external stimuli.
Until there's any empirical evidence, it isn't to be believed. "Brain waves" are not radiated from the skull. They're not even "waves" at all. There is no foundation (other than magic and faeries, kinda like the big thing in the sky that watches you all the time, even when you poo) for this kind of occurrence to stand on. It's nothing but wishful thinking.
Now, once, I had a dream that my as-yet unborn twin cousins were born with duck feet and bills. Why? Not a clue. Maybe I was watching Bugs and Daffy that day. I do have one hell of an imagination though. When they really 'arrived' a few months later, oddly enough, the skin between their second and third toes on both feet was overgrown so it almost looked like they had (barely) webbed feet. Interesting coincidence, sure. Did I predict the future with my dream? Hell no.