Creaking doors, moving tables, and hearing someone in your head seems a little tame, lol. I mean things like (group) possessions. There's a spear in my other house which is supposedly possessed by the spirits of my ancestors. Babies near it act like they're playing with someone, although, a few of them were really afraid of it.
There's stories about group possessions. There's someone I know who claims that a friend suddenly said "Set the bowl properly." He started repeating the same thing over and over, they thought he was messing with them, so they ignored him. He suddenly passed out, and another in the group said "Set the bowl properly." The guys freaked out and looked around for bowl. Turns out that the first guy to get possessed kicked a bowl with an offering some way back. The story's from a former skeptic.
How does it explain people winning the lottery right after they claim a spirit gave them the winning numbers?
It's all stories, but so are stories about robberies and snatch thieves. It's questionable, but if even half of them are true, there's some strong enough evidence right there.
If you have an explanation why, by all means say so. It could be that the very belief of ghosts makes you more susceptible to "possession". I mean, heck, typing this alone at 1.30 AM gives me an odd feeling that something's about to possess me suddenly. Could that explain ghosts jumping from one person to another, or group possessions? Regardless of culture, we all felt some odd, instinctive fear from playing Silent Hill.
I find this funny (entertaining), because you are talking about an inherently insubstantial being; they have no energy stores, no body, no brain. This means that you are incredibly more powerful than they are. Such a being could only possess you if you wanted it to happen badly, or you were absolutely sure it would happen.
Heh, interestingly, last night I couldn't sleep because of fear from this. I felt some presence wrestling with my sanity, as if trying to get control over me. Whether possession or just plain insanity, it was fucking scary. I ended up fighting the feeling off the whole night. It's not simply "letting them possess". It's like fighting the urge to stay paralyzed, trying not to go hysterical or berserk. Could be the ideomotor effect to a much stronger degree.
But being through it, I think there's a lot more control over you if you believe in it. Exorcisms seem to involve strengthening the resolve of whoever's involved, regardless of how they're performed. I wouldn't call those beings harmless. I'd compare whatever they are to parasites, physically weak, hard to detect, impossible to squash, but going to weak parts of the body.
People around here treat them like parasites too. They're convinced that there's something out there, but unsure what it is or how to get rid of them.