It's not about "natural," it's about health.
Synth's have been known to fuck people up pretty badly. The herbal blends that are so popular are not regulated so you never know what you're getting from one brand to the next, or even from one batch to the next, or even from one bag/pouch to the next. (Granted, that same point holds true with black market cannabis but it's leaps and bounds easier to correctly ID marijuana than it is to ID a synthetic that has been sprayed, absorbed and dried into a random herb.) Getting pure powder/crystals is the safest way to go about it, but then you open a whole new can of worms with regard to a synthetic cannabinoid overdose. (I'm a cautious guy if you couldn't tell

)
Dabbling in synthetics is akin to playing russian roulette with your personal well-being and, while it's
that person's place to decide whether or not they want to fuck around with synth's, you're still going to have to deal with the very legitimate opinion that synthetic cannabinoids are bad news and should not be toted as an adequate alternative to marijuana.
There's a bunch of threads about this, though. I'm not going to get into what other people have gone through-- it's already posted on the forum. I just know that those threads were fucking horror stories, dude.
I don't mean to give you shit about your drug choices, though. I'm just trying to say that I think you should be careful with that stuff, man. "Overdoing it" is ridiculously easy with synthetic 'noids.