There has been yet another study that has concluded that corn-based ethanol is bad news from a variety of angles. To quote the summary,
The study looked at factors such as the energy needed to produce a renewable fuel source compared with how much energy is produced, the impact on soil fertility and effects on food supply when fuels based on crops such as corn and soybeans are mixed with fossil fuels. Based on those factors, the authors determined that corn-based ethanol is the worst alternative overall.
The authors, research biologists, think that cellulosic and algea-based ethanol would be better, but their technologies really aren't developed yet. Here is the link to the full press release: