Effective regulations can drive illicit drugs closer to the fictional Soma, a drug that induces temporary euphoria with limited side effects (like receptor burn out) from regular use, and full recovery immediately after the use period ends. Chronic use of present illicit drugs is associated with addiction, missed work, irresponsible behavior (drunk/high driving, fighting, etc), a good recreational drug is something that someone can take at night after work is finished to feel happy, and still be able to go to work the next day and perform their jobs responsibly. Some would argue that marijuana meets this criteria, I believe that we can do better.
This is an example of a situation where regulation, rather than deregulation is desirable. MDPV is a perfect drug from a free market perspective, the drug is cheap to make, the therapeutic index is such that lethal overdose is infrequent, and the manufacturer gains a repeat customer every time his marketing material convinces someone to try it, as rat studies show that MDPV is abnormally addictive, even when compared to other addictive substances. Generally speaking, business that can sustain their revenue over time are the best business, and subscription-based businesses generally sell very well. So from a purely lassiez-faire standpoint, euphoric recreational drugs will tend towards MDPV-like characteristics without regulation. Ergogenics may not show this same trend as dramatically, because of features of the customer population, but the incentives on an unregulated manufacturer are the same.
The negative effects of drugs in the individual can be addressed by engineers. The lesson of "Bath Salts" like MDPV is that it is possible to engineer drugs with a wide variety of effects, some of which are far worse than others. If drug companies are handed the opportunity to take over the US market for recreational drugs by developing safer alternatives to the ones presently on the illicit market, they will do so with enthusiasm.