In summary: Unsustainable business practices that cost tax-payers and the towns Wal-Mart squats in serious money. Systemized discrimination. Rampant outsourcing. Unemployment. Non-livable wages and no health care for it's employees.
I recently finished a speculative fiction book by John Barnes called Mother of Storms. It's about what happens to hurricanes when the planet's oceans warm up - they essentially become bigger and more destructive and longer running and less predictable than regular hurricanes. The story explores these differences by tracking Hurricane Clem, the first to begin behaving this way.
Walmart is the corporate equivalent of Clem.