They're not, really. Not on the HFT landscape, anyway. It's tempting to say they're being slept on, but the cream rises to the top VERY fast in HFT--there have been multiple instances of products brought to market and the company being purchased outright by the first would-be customer (although this is much, much more frequent on the networking and hardware sides).

I think the analysis and borderline-accusation of what is termed "insincere quoting" by the exchanges is... laughable. It doesn't speak well to the authors' knowledge of their industry. I've had an exchange disconnect my session for sending 1000+ orders per second by myself, and I would have been quite happy to execute any of them (or else they wouldn't have been sent). To be honest, I'm surprised 5000 is the biggest number they could find. I would have guess an order of magnitude higher.

What happened on 5/6 was that the NYSE finally learned that they aren't the boss in the equities markets anymore. Trying to slow down trading without regard for the other routing destinations was nothing but quaint.

You know those videos you see of suburban shoppers at 6:00a on Black Friday, rushing through the doors to get one of the three available Xbox 360s or whatever? The NYSE was the hapless security guard whose watch was slow telling everyone the store wasn't open yet.