The direct-to-consumer marketing of stem cells for unproven therapeutic uses has grown rapidly in the United States in recent years. This development is surprising since the marketing and distribution of human cell-based medical products is stringently regulated in the US. This essay describes ambiguities, gaps, and inconsistencies in the current regulatory system that have enabled such businesses to thrive. In addition to directly challenging the authority of the Food and Drug Administration (FDA) over autologous cell-based products in the courts, stem cell marketing firms have also identified and exploited regulatory loopholes, such as the same surgical procedure exception, which exempts from FDA oversight human cell-based products that are harvested and reimplanted in a single procedure. Many businesses also advertise stem cell clinical studies on a pay-to-participate basis, which requires patients to pay large sums to enroll in clinical research. This business model not only shifts many of the cost and risks of medical experimentation from providers to patients but may also indemnify sellers from fraud litigation. Lastly, stem cell advertisers borrow heavily from the language and concepts of science-based medicine in their marketing. The inaccurate promotion of autologous stem cell injections as a form of "personalized" medicine lends a veneer of credibility and precision that may encourage patients to undergo procedures of uncertain effectiveness and to sympathize with stem cell businesses in their efforts to evade oversight.