Thanx Al-kaholik,
That's residual haunting for you.
We have energy flowing through our bodies.
Who's to say that some of that energy doesn't stay behind.
Lets say, my uncle loved to watch TV in the living room.
And would walk back and forth in the living room for what ever reason, every day and night.
Who's to say that what ever energy we have isn't left behind in a place highlly concetrated by our time exposure in the same spot.
So then one day after my uncle dies, I happen to see him walking accross the living room. It appears he's just going about his business.
Notice how in a lot of cases, the ghosts seem to just be walking not even looking at you.
It's like they are minding their own business, doing something like they can't even see you.