We know where the E. coli comes from. The culprit in the recent spinach outbreak is cow manure from a farm half a mile from the spinach fields. I wonder if we'll see an increase in calls for getting beef off a corn diet. (E. coli O157:H7 thrives in the more acidic guts of corn-eating cows, not grass-eating ones.)
Update: I clarified that last sentence. It's the acidity levels in a corn-fed cow's stomach that E. coli O157:H7 love. A grass-fed cow's stomach is not conducive to E. coli O157:H7 growth. As such, it doesn't make its way into their manure and onto our food.