Khalil's rant on why big-box stores sap the local economy applies not only to Wal-Marts, but also any national chain stores, fast-food joints, and shopping centers. Here are the stats:
small retail stores (local) average +$326 per 1000 sq ft
large retail chains average -$468 per 1000 sq ft
fast-food chains average -$5168 per 1000 sq ft
shopping centers average -$314 per 1000 sq ft
These numbers in red are deficits passed onto the local taxpayers, mainly in the form of road building and maintenance and crime-related costs. Never mind all the other dollars lost from not using local vendors and suppliers such as printers and advertisers.
Some links:
Local ownership pays off for communities
As police costs rise, towns reconsider big boxes