WalMart had the opposite effect on the city I came from, which had a population of about 12700 people. All the large shopping centers had died as the city was in decline in population, and financially. Wal Mart took over one of the soon to be abandoned big boxes (woolco) and gave shoppers a place to finally be able to buy things again. The store actually caused the population to rise again, and created a hundred permanent new jobs, not including construction, roadwork, etc...
It had no real effect on the small businesses and mom and pop stores. You want a car stereo, nobody buys them at WalMArt, they buy them from the Car Audio store because they have better product. Same goes for TVs, furniture, etc... It all boils down to the consumer. Idiots will buy everything they can at Wal-Mart and it will be for the most part, junk. People will buy thier pop, chips, candy, soup, DVDs, etc... The only small businesses that failed would have in any case (open a specialty store selling Neon and blacklight crap in a small farming community, you will fail..)
I've worked for WalMart for 7 years now and for the most part, the employment there is great, decent pay (especially for the little work they expect of most staff) and the benefits are there. I have issues with the corporate pay structure, and advancement has been tough for me as my managers have always tried to keep me handy because of my high productivity numbers. I get at least twice as much done as required, so it's really my own fault. It's basically the reason I'll leave, I should be in upper management by now but I'm still not.