It's harsh on the lungs, which doesn't do your pulmonary system any good. And it often has been grown in big fields in Mexico, where goodness only knows what sorts of pesticides have been used on it. Sometimes various types of light moisteners/adhesives have been sprayed on before the brick compression. Plus it's seedy and twiggy and, well, not great stuff. My long-time friend Lewis, a former neighbor of a big marijuana farmer in Mexico, said that after watching that process a couple of times, he'd rather smoke nothing than smoke schwag.