http://www.ethanol.org/index.php?id=50&parentid=8#E10
I'm a skeptic until proven otherwise. Bloomberg is an OK source of information, but their focus is economic and of course is capable of being biased. According to this source E10 is used in 46% of the U.S.' fuel. Also, of course direct contact with rubber engine parts w/EtOH would degrade them, but I've yet to hear of a case where E10 fuel has caused major issue except in high performance Marine Boating.
I see your point of view, and you could be right at the end of the day. However, with changing U.S. fuel regulations it may not matter because we might be stuck with E10 fuel for good.