Of all the various forms of spirit communication, I would consider automatic writing and "channeling" the most potentially dangerous forms. Channeling is, in effect, possession. It's possession with a purpose. Channeling in performed by a person who typically, has good natural psychic abilities. The goal behind channeling is to allow a foreign spirit to actually possess, or take over, the receptor for the purpose of direct verbal or written communication and on rare occasions, in demonology aspects, to enable a direct exorcism of the foreign spirit. Automatic Writing is, in most aspects, the same as channeling. The receptor allows a foreign spirit to enter him or her to enable it to directly write out its thoughts or comments. Neither channeling or automatic writing should ever take place without experienced supervision, because it is actually a form of possession, someone should always be available to help should anything go wrong. At times however, either of these can happen spontaneously to an inexperienced psychic who has not learned how to "shut down" when their gifts are not needed.
Channeling and automatic writing can be extremely dangerous to the individual because when they are "under", they no longer have control of themselves, they are now being controlled by the possessing spirit and I've seen others get attacked by the channeler while they were under. If, even for the purpose of channeling or automatic writing, a person were to be possessed by an inhuman spirit either by choice or because the inhuman spirit posed as something it's not and no one caught on to that fact, the channeler is in grave danger if it cannot be removed promptly. Even human spirits channeled in can become stubborn and decide it doesn't want to leave when you want it to.
If conducted properly and experienced people are available to assist, channeling and automatic writing can provide a wealth of information surrounding a haunting or investigation. I've seen people, through these means, obtain information that, first off, they could have never known, and secondly have proved invaluable to getting to the root of a problem, enabling a resolution to take place. It can be a great tool if all precautions are taken, it can be disastrous is done fly-by-wire or with no preparation or assistance.