From Dave Pell's great daily email newsletter, NextDraft, this report on Mother Jones that Walmart is making a lot of money for very few people:

...the six Walmart heirs now have more wealth than the bottom 42 percent of Americans combined, up from 30 percent in 2007. Between 2007 and 2010, the collective wealth of the six richest Waltons rose from $73 billion to $90 billion, while the wealth of the average American declined from $126,000 to $77,000 (13 million Americans have negative net worth).

For more Walmart related charts and graphs, check out their series on just how big Walmart actually is.