Felix Salmon (where I first saw this) draws a fine, if obviously belated, conclusion from the madness:
It’s certainly fair to say that if you take a long, five-year view, then you can see a clear rise in trading activity. But it’s also fair to say that there’s something quite literally out of control going on here…. Back in 2007, I wasn’t a fan of a financial-transactions tax; today, I am. And this chart shows better than anything why my opinion has changed. The stock market is clearly more dangerous than it was in 2007, with much greater tail risk; meanwhile, in return for facing that danger, society as a whole has received precious little utility…. The stock market today is a war zone, where algobots fight each other over pennies, millions of times a second. Sometimes, the casualties are merely companies like Knight, and few people have much sympathy for them. But inevitably, at some point in the future, significant losses will end up being borne by investors with no direct connection to the HFT world, which is so complex that its potential systemic repercussions are literally unknowable. The potential cost is huge; the short-term benefits are minuscule. Let’s give HFT the funeral it deserves.Um, to say the least.