Over on the Spiritus Mundi yahoo group, the topic of the dangers of magic has reared its fearsome head. It started with an Algol talisman, which Chris Warnock discusses in this post. To summarize, someone used a rootworker's technique with a traditional astrological talisman, and it backfired. They made an Algol talisman to ward off any magic worked against them, and then buried it where they ran into their main enemy the most. After this, they experienced a run of bad luck, and it was determined that the spirit of the talisman was upset because the magician had used the talisman wrong. (You're supposed to wear the talisman, not bury it.)
The analysis of the problem seems legit to me. It passes the book-check (sources support that the use was altered) and it passes the common sense check. (Medusa can be a touchy spirit to work with. She's got snakes for hair, you know.) And screwing around mixing up traditions and approaches can be dangerous. You get unwanted effects. You suffer maladies. You get ill, you lose your job, your relationship hits the rocks, your car breaks down, and your kids talk back, with intent.
This experience prompted a Palero on the list to point out that MAGIC IS NO JOKE! and that is why you follow the instructions. Magic is real. It does stuff. It's not all pretend make believe that doesn't really change anything but your feel-feels. Magic works. That's important to remember.
John Michael Greer then wrote a post full of wisdom and common sense, exhorting people to follow the instructions we are given in traditional resources. He made an analogy between electronics and magic. You would follow the warnings and recommended techniques of an electrician when wiring a circuit, wouldn't you? It's your best bet to avoid electrocuting yourself or burning your house down. (I'm paraphrasing, except that last bit, that's a direct quote.)
I agree with him. Speaking as someone who burned their house down using demon magic that went wrong, I have an informed opinion on this subject. You really can burn your house down using magic. My house fire was the result of a really poorly phrased statement of intent, though, not a poor technique. The technique worked great, honestly.
The statement was fucked. "Get me the money by any means necessary, just as long as no one in my family gets hurt." That's a TERRIBLE way to do magic. It (probably) wouldn't matter if I'd said that to demons or angels, but the fact that the spirit I was Working with at the time happened to be from the lower spheres certainly didn't help. Angels seem to have a higher perspective based on living at a bit more distance from the hands-on material world than Bune does, but that doesn't mean they won't burn your house down to get you an insurance check, and prove a particular point about your use of magic at the same time.
But whenever people start talking about how dangerous magic is, I feel compelled to say, yeah, it's dangerous... but do it anyway! Burnt fingers are our primary teachers as we explore the books and figure out how it all works. There is no real life Hogwartz to attend. Some lodges may offer a curriculum that trains you in magical practice, but most are based on post-1899 magical theory. The only Order I know of that taught medieval alchemy and traditional Hermetics is pretty much defunct, and even they were open and honest about how they were experimenting and figuring out what the grimoires were all about on their own. They passed on the information that worked, and warnings about mistakes they made, but they were still front-line soldiers, pioneers exploring the wilderness with faulty maps and compasses that didn't always point North.
Modern magicians interested in learning how to do the magic recorded in the Picatrix and Agrippa's Three Books are going to, by necessity, have to explore and cover ground that hasn't been covered in recent history. Even the most comprehensive and detailed grimoires have gaps. The context of some of the manuscripts we've received is lost to history, and we're left to argue over whether all the spirits of a manuscript are called into Triangles of Art, or only the ones that specifically mention the Triangle.
Personally, I've never done anything with magic that messed up my life so badly that it couldn't be fixed with magic. It's dangerous, yes, but that's what makes it an adventure. Have courage, be bold!
Just be rational about it. Heed the warnings of those who have been there and done that, follow the instructions.
But don't be afraid to have fun.