Some companies have discovered, to their surprise and profit, that programmers are very creative people. I think of Google and Atlassian, for example, who allow regular (monthly, I believe) "free days" where programmers get to work on whatever they want (with approval) and the company reaps the rewards. Examples cited were new products, bug fixes that no one had wanted to fix before, new teams forming, etc. Another result (and perhaps the original goal) is that for the remaining days between free time programmers have more motivation.
Is there more backing to this theory, that allowing a "controlled" creative output is good for motivation and morale, or more examples of successes with this approach?