There are far too many reasons to list why Walmart should be boycotted. I urge you all to take a moment and read up on some of the problems here:
http://walmartispureevil.blogspot.com/
The blog does a good job of bringing all the problems of Walmart into light. Bearing in mind that there is a bias agaisnt Walmart, outside research could be done to verify the claims in the blog.
Some immediate effects of having a Walmart open near your home is a decrease in property value, as well as increased crime. The home you spent so much money on is now worht significantly less, and your neighborhood will become less safe.
Walmart is also an absolutely terrible company. The evils committed by Walmart are some of the worst instances of corporate abuse in human history. Do your part to stop the madness and boycott Walmart.