I think your reply deserves a spotlight. By holding up your employment situation as an example, you've at least cursorily defined most of what makes a good tech employer to a T. One of the key ingredients, I think, is that the employer makes learning new things a desirable activity for its employees and fosters that. There are few ways to do this that compare with the "work on open source software projects when you're not on deadlines" approach. I think that really the most valuable aspect of Google's 20% time isn't the new projects and "products" that employees generate, either: it's the fact that it fosters, encourages, and supports learning — and makes that learning desirable to the employees in a way that "paid training" and similarly institutionalized corporate initiatives don't.

Bleeding edge technical industries, which covers almost everything related to computers these days, thrive on new knowledge. The core issue of this entire discussion is that tech employers need to harness that new knowledge phenomenon. The things to look for are people who learn about the field on their own time because they like it, because they want to know new things, and because the way they're wired you couldn't get them to stop learning and tinkering short of inducing burn-out. The things to do involve providing inducements and environments encouraging that learning, and the things to avoid doing are those stultifying bureaucratic and buzzword-compliant procedural things that contribute to burn-out and a feeling of oppression.

Autonomy is really one of the key ingredients to this. The only other such that comes to mind is creating a work environment where the employees don't have to worry about anything they're not getting paid to do. If you're working sixteen hour days to meet a deadline in an office building, for instance, the employer needs to find ways to address concerns like childcare, hot meals, and the like, so that the employees don't have to, and if you're a reasonably intelligent employee that was worth hiring in the first place the management should trust you to know what you're doing, be able to organize your own time, and be able to turn whatever interest grabs your attention into a benefit to the company, even if the primary benefit of it is just keeping you sharp.

Unfortunately, American corporate culture is pretty much diametrically opposed to these characteristics of a work environment that are most conducive to acquiring, keeping, and improving on quality employees.