I subscribe to the Religion News Blog, which should be no surprise to anyone. As I scan the headlines, I see a lot about court cases and murder charges. Parents who starve their children as some kind of penance. People drowned as a result of some bizarre exorcism ritual. Most recently--a mother who burned her daughter as part of a voodoo ritual.
I think about this kind of thing in the context of folkloric "satanic" rituals, in which you get groups of people killing animals, or occasionally you will find a human being supposedly killed for such reasons. Like Lovecraft's "Necronomicon", there are a lot of people who believe that this is "real" magic. (In case you don't know--the Necronomicon is a fictional invention, but many people think it is a real occult grimoire).
This idea is a very old one in religion--bloody sacrifice is all over the Old Testament, and all religions have had some version of this in their distant past. In modern times it is often associated with black magic. The attribution, if not faulty, is unnecessary. A.E. Waite traces the idea of a "sacrificial victim" in black magic to a simple functional need--blood was not required for the ceremonies. Pacts required a written document, and it wasn't that easy to procure the right writing implements. So--the magician often had to slaughter his own lamb and tan the skin for this purpose. In modern times, assuming one would want to do such a ritual, the magician certainly has fine parchment and vellum at his or her disposal without going through that trouble.
Outside of the idea of "pacts", there are also old "natural" magic rituals that may call for the blood of an animal, or maybe even of the person. However, for those practicing today, there are obvious substitutions. Just as various herbs and essences can be substituted in incenses and oils for various purposes, those ingredients obviously can be dispensed with as well.
Blood is associated with life, and hence with one's "manna", or power. This at least is part of the psychology of its use. On the other hand--I've heard Swamis who refer to blood offerings (in this case to Kali) as being "impure". Blood is associated with the temporal body rather than the eternal soul. Hence, one should not offer blood, but true devotion.
For all this, you still hear about bloody sacrifice. It's probably not as prevalent as you would think; like many things, the media will tend to focus on the shocking, and treat it like it's the norm. Sacrifice is probably most prevalent today in traditions like Santeria (a sort of Catholic voodoo), in some tribal religions, and in small villages in Asia. Kali worshippers in rural parts of India are said to occasionally perform sacrifice--sometimes you even hear of a Tantric priest sacrificing a child. Amma has said that such practices are based on a misunderstanding of Kali. She is not a violent force to be appeased--she is the root of Consciousness, and as such, is very intense.
Intensity may be the key regarding such practices today. We live in fear of the Numinous, and we feel it has to be approached in grave ways. This is why you will not only see the idea of bloody sacrifice, but the need for very expensive tools in magical practices (e.g., sigils made of solid gold). Someone asked Lon Milo DuQuette about that very thing at his lecture on Goetia. Lon's response to the idea of gold sigils for demons was, "they're lucky if they get cardboard". The reality is that none of these things are necessary. It says more about the insecurity (and perhaps the inexperience) of the magician in question. Which goes back to something else said by Lon--in order to practice Goetia, "one must be a Solomon". Which means you have to be in control of yourself and willing to face the unknown with confidence. Often there isn't perfect confidence, so one needs a lot of fancy trappings to make oneself feel "like a Solomon".
Magic of any type is psychological, and as you know, that doesn't reduce or minimize it. It is highly symbolic, and all that matters is that you are able to connect with the symbols you are using. I remember a witch telling me once that you could do a Wiccan ritual with a feather, a match, a coin, and a drop of water (for each of the elements). When you examine the universe, it becomes more and more granular, until you realize there's not much to it that's "real" at all. When we take ourselves and rituals too seriously, it is because we are completely taken in by the illusions around us. One of the most fascinating things about psychology is how something can exist independently of you, but also be "just in your head" at the same time.
As humans we like illusions. We tell stories. The whole drama of our existence is based on stories. The scarier things sound, the more expensive things are, the more authentic they must be--they must be "better" or more "real". It's amazing how much time and energy we waste on that kind of absurdity. Often the only real thing is fear is such cases. But all of us are affected by it unconsciously.
A final thought--most of the Adepts that I have met over the years are people who didn't (or don't) take themselves too seriously. Being around them is like being around the Satguru--they radiate a joy and peace that comes from understanding in a real way (not just intellectually) that Life is a drama, and should not be approached in such a grave manner. And of course, the more ego baggage we lose on the journey, the more we find that rituals are at some point unnecessary for us. This is true of religion as well. Amma has said that rituals and deities and images are "ladders that we climb to reach our destination"--but they are not the destination. That said--the mind does work in images, so images will always be with us.