Excellent thread OP.
I have often wondered and asked the same thing. My house has spirit's. One grounded and many other's just hanging and then leaving. I live just outside of Washington, DC and have seen a full figure Civil War man apparition. My house was built on a stream and my grandparents were the original owners; both died in the room I sleep in at night-- years apart from one another. I have a couple threads regarding this but no real responses/help/knowledge towards my predicament.
I also live across from a 70 acres open field that is the home to 4 huge radio transmitter towers 6,000 watts AM directional signal. I personally feel that I'm sitting on some sort of hot spot. A friend of mine is an anthrpological archieologist. She has helped me with the history of the land and that my home is built on a stream.
I also garden. The reason I bring this up is because I'm always digging up lumps of quartz (lol I now have a rock garden too from all of the stuff I've dug up). My son and I even got into rock tumbling and some of the peices are beautiful. Anyway, I truly think the combination I have going here is something. Oh yea, I also call my house the "spirit party house". No real danger and nothing negative.
Outside of my immediate family, I've had over 15+ witnesses of at least one of my spirits. ((One time it was a friend of my daughters at a sleepover

- not a cool night for that poor girl!)) Anyway, I usually do not speak openly about this (except on this forum) so not many know; outside of random witnesses and of course other family members who lived here before me.
Thank for the thread. Hopefully I'll learn something new

Take care

Jody
edit: speeeeeeeeeeeeeeeeeeeeeeling