That's one of the CDC's top lessons from the 2009 E. coli O157:H7 outbreak in refrigerated Nestle Toll House cookie dough products. During the outbreak, 77 people in 30 states became ill after eating the dough before baking it. Of these, 35 people were hospitalized. The outbreak prompted a recall of 3.6 million packages of cookie dough and some changes in the way that Nestle and other companies manufacture their cookie dough.  So, yeah, pretty bad, don't know what changes were made though.  Edit: looks like they switched to heat treated flour to stop this happening.