— Kevin Drum of Mother Jones fires back at Megan McArdle and Matt Yglesias over interchange fees.

… on the list of ways in which the poor are screwed, this doesn’t make the top ten. It probably doesn’t even make the top 100. But I hate the idea of dismissing it anyway. The problem is that this is practically a paradigm example of how all this screwing works throughout the financial industry: most of it is small stuff. It’s a few dollars here and there, and banks have a huge incentive to keep it that way. That way nobody really thinks it’s worthwhile to bother addressing even though those dollars add up to billions if you screw enough poor and vulnerable people at a time. And Wall Street does. That’s why this kind of thing deserves attention even if it’s not, by itself, all that big a deal: because there’s a lot of it, and it basically all benefits the haves at the expense of have-nots.

Ryan Chittum is a former Wall Street Journal reporter, and deputy editor of The Audit, CJR's business section. If you see notable business journalism, give him a heads-up at rc2538@columbia.edu.