Walmart is out with one of those corporate ad campaigns where some tiny fraction of one's purchases will go towards some pressing issue. This time it's hunger, so the money will go to support food banks. As far as corporate pseudo-charity goes, one could certainly do worse. But there's a much more useful strategy Walmart could employ, and one that would actually boost its bottom line: Use its massive lobbying heft to push for increases in food stamps. Here's the ad: It's equal parts genuinely aimed at an important issue and patently unrealistic.