C'mon now. It's not hang-gliding or dropping acid, it's sitting quietly in a room. Not everything in life should be treated as if it's horrendously risky or can't possibly be understood by people exercising common sense.

Nor, in my opinion, do the agglomeration of various meditative practices and teachings, no matter how old and "sacred" they may theoretically be, necessarily have anything all that critical to add to the subjective experience of simply sitting quietly. Just like the practices and teachings that accompany many organized religions, a lot of meditative lingo and theories about meditative "progress" is, IMHO, horseshit peddled by people who have decided to make a living selling said horseshit or have defined themselves by their unquestioning acceptance of said horseshit.

edit: I should add that I can recognize that, as others discuss in this thread, deep meditation over long periods may trigger various psychological issues for some people. However, it's also true that, for example, eating food can be extremely problematic for some people who have serious eating disorders. That doesn't mean that the mere act of eating, which most people manage to do just fine, somehow needs to be guided by some deep tradition, and I don't believe that sitting in meditation needs such guidance in general either. For most people, meditation is a very gentle, mildly restorative practice that aids mood and focus, not some metaphysically shattering cataclysm.