You made a very, very interesting post there Phobotech. I am very interested in ghosts of all kinds, I even find myself interested in the kind I know aren't real - Folklore is something I'm fond of. I have often wondered about communication with the dead as well and I think it is very possible and I have something you may find rather interesting regarding why I believe so strongly in that possibility and it ties into my experience with a ghost.
I have lived between two places most of my life: Birmingham in the UK, and Shirakawa village in Japan. I was born in Birmingham and spent the first 6 years of my life there, and spent most of my life in Shirakawa and actually still live there with Chie, my wife, who was also my best childhood friend. Growing up, Chie & I had a friend who claimed to live in a haunted home. Chie & I would spend nights there, "ghost hunting" and we actually had quite a few 'experiences,' but needless to say we were only finding what we wanted to and facing our wild, 7 year old imaginations. With one exception.
During one of our sleepovers, I awoke late and saw Chie was up too - she was praying (She is very devout in her countries old religion of Shinto) and needless to say, I found it strange. She told me that she saw a sad old lady, who she claims told her we were being disrespectful with our silly "ghost hunts." Chie said she had never legitimately encountered a spirit before and felt bad about how we were acting in what was her home. That whole night, and on into early morning - I felt as though I was being watched by a calming presence. That morning, the phone rang and our friends parents read the calling phone number aloud (This is actually an important detail) and I quickly identified it as my mother, back in the UK. During the conversation, I noticed something odd - an old lady whom I never saw walked by me and sat on the couch before vanishing. It had a strange look, it wasn't solid but it didn't look fully transparent - it looked almost like a shadow made of crystal, in an odd way it was quite beautiful as the light shined through it. I hesitantly described what I saw to my friends parents, they said that it sounded as though I had met Haruki - my friends great grandmother.
Fast forward almost 4 years. Our friends moved out of that home, and I was going to Birmingham for a couple weeks as my mothers lover Meranda (I was raised by a Lesbian couple) had fallen deathly ill. I had to help mum take care of her, often times while mum was meeting with her patients. One day, the phone rang. The caller ID claimed the call was coming from Japan, but it wasn't Chie or her families number. I ignored it. It called again 5 minutes later, and this time I picked up just in case Chie was calling from somewhere else. I heard a male voice, one I had never heard before - he seemed confused, and then he asked if it was the Bird residence and if Kadath was available. I was a bit disturbed, to be honest - but I am not the kind to lie, so I said "Yes, you are speaking to him." The man on the other end said "I think I'm going mad, but I keep hearing an old womans voice. She gave me your number and told me to warn you that Meranda is not breathing." I immediately put the phone on hold and ran downstairs to Meranda's room, she was indeed not breathing save for a labored gasp every now and then, I could not wake her but she was still alive and so I called emergency paramedics, and saved her life. I thanked that man, and told him to thank Haruki. He said "Dear god, this is insane - but you are welcome." When we returned to Japan later that year, I went to the house - and sure enough, the man I had never met before was now living there. He had moved in a week after I left for the UK.
It was easily the strangest thing that ever happened to me, but ever since I have believed in ghosts and like you Phobotech, have wondered about communication with them. I at first wondered why Haruki couldn't contact my directly if she could know such information, but I then saw a documentary on ghost theories and was interested by one that suggested that ghosts can not leave the place in which they died but can gather information through electric currents, and may even operate on such currents - areas with higher concentrations of television and radio waves and the likes often seem to be places in which ghosts are most often reported. I'm sure you are already aware of this, as you referenced it in your post.
Figured you might find that interesting. Thanks for putting up this post, I shall have to read some of the other peoples experiences.