The Monitoring the Future study has added the synthetic marijuana products (see here, here, here for additional) to their annual survey. Data on annual use rates are now available for the 12th grader segment. I have taken the liberty of graphing the annual use rates for a selection of the more common drugs in this 2011 dataset.
What you can see (click on the graph to see a bigger version) is that these products are more popular than a host of drugs that have a considerably longer history. These packets of plant material spritzed with one or more full endocannabinoid CB1 receptor agonists (see dr leigh here, here for details) only really appeared on the US market in 2010 in broad availability.
Not too shabby to already be beating these other drugs, eh?
Unfortunately the full monographs aren't available yet and the update tables for "lifetime" and "30 day" do not appear to include the synthetic marijuana category yet. Nevertheless, it's a good thing that this drug category has been added to the survey. As we go forward it will be interesting to see if popularity continues or if this was a brief flash in the pan related to broad quasi-licit availability of these products.
These data will also provide a nice comparison to more limited investigations such as this one. Hu et al (2011) report 8% cannabimimetic use in a sample of 852 college students collected in September of 2010.
The Annual Prevalence table is here.
MtF 2011 update page