The most recent issue of the NEJM, here discusses the globalization of clinical trials.
Concerns noted in the article include:
Wide disparities in education, economic and social standing, and health care systems may jeopardize the rights of research participants;
There may be a relative lack of understanding of both the investigational nature of therapeutic products and the use of placebo groups; and
In some places, financial compensation for research participation may exceed participants' annual wages, and participation in a clinical trial may provide the only access to care for persons with the condition under study.
Worth a read.