Here is a nice interview a local TV station did with my friend and colleague Dr. Michael Edmond about using fecal transplantation to treat Clostridium difficile infections.
Clostridium difficile ('c dif') are bacteria that can cause diarrheal disease; a major risk factor for developing infections with these bacteria is previous antibiotic exposure. In the presence of antibiotics, these bacteria have the opportunity to outcompete the gut's normal bacteria, take over, and cause disease. These infections are associated with significant morbidity, and can be deadly, as well.
Although antibiotics can be used to combat these infections, some people suffer from recurrent infections despite antibiotic treatment. Fecal transplantation replaces the normal bacteria that are lost, and has been associated with high cure rates for patients who have failed other therapies.
The above video is well worth taking a look at.