At The Milkweed website is the entire complaint filed by the Department of Justice against Dean Foods.
Here is a small but, telling part:
42. The Acquisition will result in a substantial increase in the concentration of processors that compete to supply fluid milk to purchasers located in the relevant geographic market. Some of these processors are located outside of Wisconsin, the UP, and northeastern Illinois. Prior to the Acquisition, Dean had the largest share of sales to purchasers within the relevant geographic market. Dean accounted for 44.6 percent of fluid milk sales; Foremost accounted for another 12.6 percent. As a result of the Acquisition, Dean now has more than 57 percent of all fluid milk sales in the relevant geographic market. There are only two other competitors with more than five percent of fluid milk sales in the relevant geographic market, Kemps LLC (a subsidiary of Hood LLC) ("Kemps") and Prairie Farms Dairy, Inc., which have 17 and 15 percent,respectively. Moreover, Dean's post-Acquisition shares are even higher in certain areas within the relevant geographic market: over 85 percent in the UP and over 60 percent in Green Bay, Wisconsin, and in northeastern Illinois (including Chicago).
Dean Foods has vowed to fight: http://www.deanfoods.com/our-company/news/press-release.aspx?StoryID=1378120
Dean feels the purchase will, "spur competition in and around Wisconsin."