Watch Walmart: The High Cost of Low Price for reasons why WalMart is evil.
Cliffs:
WalMart:
Pays lower wages than other big box retailers.
Refuses to allow many employees to attain full-time status.
Cheaps out on heath care and benefits, instead relying on state and federal programs to support its workers
Obtains free grants/incentives from local governments to set up shop, to offset land, zoning and road costs, etc. Local businesses do not get preferential treatment.
Drives out local businesses, causing unemployment.
Has set up in towns and then left shortly after before repaying loans, etc.
Disallows unions.
Is discriminatory in its employee advancement practices (e.g. glass ceiling for women)
Imposes censorship on media products (music, movies, print) it sells.
Essentially, Wal-Mart is heavily subsidized by local, state and federal governments, which is one of the reasons it can offer such low prices.
These concerns are in addition to the common complaints leveled at big-box stores - environmental concerns, traffic and vehicle use, supporting abusive suppliers in developing countries (e.g. China).
I don't know if Target is involved in any of the specific practices I mentioned, but I can tell you that, for example, Costco is a big-box retailer which is not guilty of those Wal-Mart specific practices - only the basic problems with big box retailers.