We're a small company of 40. If someone wants to take time out to learn something or try an idea or work on a project of their own then they should do that. We don't allocate a specific portion of time to do that but we don't measure hours worked anyway. We only measure what people achieve. If they do meet company objectives by only spending half a day a week hacking on "directed" work then that's great. More time for them to invent something really cool. It helps that everyone in the company has equity and feels like a real owner which means timewasting and abuse is quickly pointed out and stopped.

I'm the CTO. Feel free to ask me anything about the culture we have.

Kiva is a small non-profit of about 70 employees. Not only do we have 20% time, we have it as a full 2-week iteration where we can work on anything we want. It's awesome.

I'd be surprised if it was common... if you think about it, startups are basically "20% projects" that everyone in the company is spending 100% of their time on. :-)

I've heard that ReadyTalk, in Denver, offers it in the form of "eight weeks on, two weeks off" scheduling. A couple of friends from work have interviewed there and said that it seems to be a great motivator for the engineers.

One even rigged up an iPad to their in-house keg that somehow analyzes pours and is working on the "perfect" pour for each beer.

It's no longer a small company, but I was reading today that SpaceX encourages it, on a "one full week out of every five" basis.