But that's not the same as putting small businesses out of business...

"Critics of Wal-Mart and some academic studies, particularly out of the University of Iowa, claim that Wal-Mart displaces locally-owned stores resulting in the reduction of locally-owned corporate assets and real estate, and the destruction or displacement of higher paying jobs. Other studies, including several recently from the University of Missouri, have claimed that Wal-Mart stores either do not have negative impacts or have been found to positively impact a community by effecting lower prices, increased employment, and increased establishment counts."
http://en.wikipedia.org/wiki/Wal-Mart

Obviously this topic is so controversial that one may question the accuracy of the Wikipedia article...