Well, clearly most of the traders weren't profitable and pulling their weight - but that is symptomatic of the prop desks throughout Chicago. Even DRW really pulled back on campus recruiting and consolidated office space. I can't think of one firm that didn't downsize to some extent - most were dramatic.
It used to be that firms would keep mediocre traders on because they generated some commission income and desk fees - but the past few years those types couldn't keep it between the ditches. Even the guys with arbitrage opportunities watched them dry up in days when they used to last for months.
I can tell you that my personal trading style has changed dramatically. Seven years ago I could easily trade 200K RTs per month on average. These days I'm taking orders of magnitude fewer trades and sitting with them far longer (hours for God's Sake - maybe even a day or two!) in order to preserve an edge and keep clear of the HF turbulence. Seems to be working.
Based upon the client load I have taken on, you have size spread traders getting their collective asses handed to them trading mean reversion in clearly trending markets, and you have size directional-position traders constantly getting shaken out of stuff and chopped to bits in the process.