Hi Emil
A short answer is "the crown is relatively easy to open but when you do, many spiritual issues/karma could be released causing depression, psychological imbalances and the like". It is so easy to activate that just working on the brow chakra will indirectly cause the crown to become more active. However, if you succeed in opening the crown without issues or imbalances, the warning to stay away from the crown can probably be dismissed. I find that if I work a lot on the crown, it sometimes produces migraines that last for days... self-pacing is a good thing.
I have been studying the information that I've been sent for "Shaktipat in Absentia" from Shri Anandi Ma (Dhyanyogi) for a week now. I will be doing this process in the near future.
In the documents that were sent to me, it says that when you receive shaktipat, you are forming a link with a guru and the guru's energy. After that link is formed, the guru makes sure your kundalini evolution/rising is safe and doesn't harm you.
There is also a section in the notes that explains how to call the guru for help should you need it. The example they give is "if you are at work and spontaneous asanas or movements start up (shakti cleaning), you pray to the guru (3 times) to arrest the movements at that time because you are at work or driving a car.
One point of interest. After receiving shaktipat, you are supposed to meditate 1 to 2 hours a day for 10 days straight. During those 10 days vegetarianism and celibacy is preferred. It warns that if you are not celibate for at least 10 days after receiving shaktipat, you could lose/dissipate the energy that was transmitted to you. Also, if you do not follow their directions, it says that it will slow down the rising of the kundalini to the crown and it could take months or even years before kundalini reaches the crown. However, there didn't seem to be any danger associated with a lengthy rising process.
If your third eye is open you can see beings from other planes and from this plane. If you meditate on these beings you can receive guidance and wisdom from them (or not). Several times when I've been reading various books, the attending guru has appeared to me. I also see Jesus anytime I wish because he is always there. So, it is quite believable (for me) that when receiving shaktipat from a guru you will also aquire a new family of beings that will watch over you, protect you, guide you and help you on your way. That's how I perceive it.
On the other side of the story, kundalini is actually the rising of the vast storage of prana in the root chakra to the crown. It is like your body is a long bar magnet, and, after cleaning out the pathways in the middle of the magnet, the polarities collapse or join.
Picture, if you will, the body as a bar magnet; the head as the positive charge and the root as the negative charge. If neither location has very much charge there is little flow between them. If the center of the magnet is blocked or impure, there is very little flow between the poles. If you increase one or the other or both poles's charges, it strenthens the overall magnetic field between the two poles, but this depends on the clarity or openess of the pathway in between.
If you increase one or the other or both's poles' charges and clear the pathways in between, the system eventually collapses, or rather, the prana which was stored in the root jumps up to the crown and from then on, lives there or possibly in a higer chakra. Hence, the kundalini rush to the crown which is experienced as a roaring river of electrical activity rising to the crown.
If you augment the charge at the root or the crown, thereby increasing the pull on the other pole, but your central pathway is not cleared, or perhaps you've focused too much on an intermediary chakra along the way, (like your solar plexus chakra) then that magnetic pull will be drawn to that chakra, or even a location in the body. This is the cause of kundalini imbalances, and even non-kundalini imbalances (obesity, hedonism, egocentricity, materialism etc). As well, according to the Taoists, if you accidentally or intentionally take your chi into two dangerous locations in the body it will cause sickness and even death. Can you imagine what high voltage kundalini would do in those locations?
A point of interest: Did you know that Shri Anandi Ma instructs menstruating women not to physically touch her of prepare her food? It is because at that time the apana flow is greater and will cause energy loss in people who are highly energized.
So, for what it is worth, knowledge and/or a guru is probably a good thing. Receiving some energy from someone, a guru, a practice, deep abdominal breathing, correct diet etc will increase your energy. It is up to you to understand the process and clear your bar magnet yourself. And any help you can get from anywhere is a blessing and something to be grateful for.
OM Shanti
TI