It is found in several fake ecstasy pills and legal highs. There are a lot of people that have been getting bad side effects, nausea, vomiting and headaches. Sometimes they are mixed with metoclopramide in hopes it will reduce nausea but side effects increase.
I personally stay clear of these substances. I think there are way more interesting choices out there, but each one to his own. Just be safe! If you must take, be sure to analyze your product to know what you are consuming, at least buying a reagent to check for color changes. Check links in my signature.
In the information subforum, the scientific articles thread, you can see some publication just posted that goes over some of the piperazines, pharmacology, etc. Check it out.