The term guinea pigging first entered the mainstream American vocabulary in January 2008 when an article by that name was published in The New Yorker. Guinea pigging refers to healthy individuals (overwhelmingly poor, sometimes students) who participate in clinical drug trials for pay.
In the past, most participants in drug trials were either medical students and personnel who at least intellectually understood the risks they faced or persons struggling with illnesses who might benefit from the drugs they tested. Over the past 10 years, however, as drug testing and development have exploded and have largely shifted from nonprofit to for-profit operations, the need to quickly find large numbers of research subjects has led to the widespread use of healthy subjects for pay in early trials of drugs. (If the drugs prove safe with healthy subjects, they are then tested for efficacy on ill subjects.)