I wonder how much of the negative experiences people report is down to the way the products are made and the different ways that different kinds of customer use them versus intrinsic issues with the chemical itself.. It's interesting to look at the situation in the UK, where you can split synthetic cannnabinoid products into four categories: Head-shop herbal blends, online RC vendor blends/c-liquids and chemical powder.
News reports of people being taken into hospital are almost exclusively related to head-shop blends. We get occasional reports on UK-based RC forums of people having issues with online RC vendor blends - a batch of an MMB-CHMICA blend sold by one vendor seemed to cause problems due to its potency (subsequently the amount was reduced). There's plenty of people who have issues with tolerance and withdrawal after extended frequent use with any of these products. But we mostly don't have the sporadic mass poisonings that seem to be a regular occurrence in the USA. When multiple people are taken to hospital after smoking a blend it's invariably a group who were smoking the same individual packet of product together.
This suggests that a couple of issues could contribute: quality control and customer inexperience. It's likely that the UK head-shop
blends have less accurate and uniform concentration of active chemicals than the online RC vendor-stocked blends. Vendors get a significant boost to business from reputation whereas head shop blends can easily be repackaged if a particular brand gets associated with bad results. The mix-and-match approach to blend formulation and a reluctance to disclose ingredients accurately also suggest customer safety doesn't rate as a concern for the manufacturers. So head-shop blends probably vary significantly in dose (and possibly chemical constituent) both between and within batches of any particular product. Online RC vendors in the UK aren't a perfect model of integrity, but tend to operate more responsibly than the bricks-and-mortar side of the market.
The two sectors of the market also attract different customers. Users of online RC vendors tend to be older and better informed than head shop users and probably have more interest in using safely (or at least minimising their risks). So head shop customers are probably more likely to take a cavaleir attitude towards dosing while RC customers may well own scales and measure each dose. I.e. one of these customer-types is much more likely to buy a product based on its excitingly dangerous sounding name, have no idea of the chemicals involved or the amount of them, take it home and immediately take a massive bong hit of the stuff.
My own impression is that used with moderation, in a responsible and safety conscious way, and sourced from more reliable suppliers, the synthetic cannnabinoids don't stand out as particularly dangerous research chemicals. Cannabis has a history of use going back thousands of years and the kind of safety record most pharmaceuticals wish they had. Synthetic cannnabinoids have none of this and are much riskier, with a safety record that involves a small but significant number of fatalities. That risk is multiplied if the source is unreliable or the customer doesn't know or doesn't care about safety issues.
