Shared decision making in medicine has become a widely promoted approach. The goal is for patients and physicians to reach a mutual, informed decision by taking into consideration scientific evidence, clinical experience, and the patient's personal values or preferences. Shared decision making, however, is not a straightforward process. In practice, it might fall short of what it promises and might even be misused to whitewash monetary motives. In this article, which summarizes a presentation given at the 17 Annual Conference of the German Network Evidence-based Medicine on March 4, 2016 in Cologne, Germany, we discuss three contextual factors that in our opinion can have a tremendous impact on any informed decision making: 1) opinions and convictions of physicians or other clinicians; 2) uncertainty of the evidence regarding benefits and harms; 3) uncertainty of patients about their own values and preferences. But despite barriers and shortcomings, modern medicine currently does not have an alternative to shared decision making. Shared decision making has become a central theme in good quality health care because it has a strong ethical component. Advocates of shared decision making, however, must realize that not all patients prefer to participate in decision making. For those who do, however, we must ensure that shared decisions can be made in a neutral environment as free of biases and conflicts of interest as possible.