Most oil companies don't like ethanol, and I would argue they are a pretty powerful special interest group opposing any influence the corn growers might have....essentially evening it out overall.
Then why do we still have ethanol in gasoline? Why are the "flexfuel" vehicles being touted as an answer to high fuel costs? It's a matter of who has the power, and how motivated they are. The oil industry may not like ethanol, but it isn't a big deal for them.