I got some topical clindamycin over-the-counter when I was in Thailand, and it worked better than any other acne drug I had tried. I couldn't find it in any pharmacies after returning to the US, however. I emailed the FDA about it, and they responded:

Clindamycin is an antibiotic, whereas benzoyl peroxide is not. Necessary characteristics for OTC drugs include an acceptable safety margin, low misuse and abuse potential, and adequate labeling. In addition, consumers must be able to self-diagnose, self-select the medication [self-selection is the decision a consumer makes to use or not to use a drug product based on reading the information on the drug product label and applying knowledge of his or her personal medical history], self-treat and self-manage the condition for which the OTC drug is intended, and additionally, a health care practitioner is not needed for the safe and effective use of the product. An OTC drug is considered to be safe and effective for use by the general public without a prescriber's authorization. At this point in time, FDA believes that clindamycin does not qualify as an OTC drug.

I'm slightly disappointed at this decision.