Microbes are used in waste water treatment and are very effective. However in that process they are kept contained. In waste water treatment there is nothing for the microbes to eat but the organic matter in the waste water. I am uncertain as to how this would work in an open environment. How do you keep them around the oil spill site, what else will they eat in the environment, what other kinds of side effects might they cause, etc. Given our experience with them in the waste water area, it's hard to believe that if it was really viable we wouldn't have already implemented it.