I have always wondered if in-house work is legitimately more boring or if the goal of working at an agency has just been drilled into them since design school.
Is it considered a stigma on one's resume to have done in-house work? If not, it seems like designers could go for the programmer model of employment -- work in-house for a few years then switch to a new place for new challenges when you stop learning and growing, unless a new challenge is presented.
My wife is just moving from being in-house to an agency, but these are in huge demand for beijing.
I'm also seeing the same talent flight as the author of the piece, not just with designers, but also devs and good producers/project managers. At some places I've seen, companies avoid certain clients because they fear poaching by their own client(!) Is it too conspiratorial to think that talent-hungry clients are doing trial-run projects to try out and entice potential employees? A couple years ago, I would have thought that was crazy. Now I'm not so sure.
My personal opinion is that a shakeout in this/these industries is coming in the next few years. That tide goes out, and a pile of firms will go with it. There's no way the numbers are sustainable. Something has to give here.