Seeing as no one's replied yet, I'll add my 2 cents:

My first reaction is it sounds like a cross to the dream world, which can happen when you're awake and pretty easy with brainwave altering stuff playing. It's happened to me a lot, not necessarily thinking I've seen someone, but subtle things like curtains blowing with the window shut.

These videos are a lot like that, they can open you up psychically to a range of things. It helps with OBE's, and perhaps your friends' brain is not used to this stuff, in which case it can activate things they're not used to.

Hope that helps somewhat.