[billnguyen]

As a former Googler definitely agree with the 120% time. But I think its more because its hard to do any work effectively only once a week. So in order to make your 20% time be useful you just have to put in more time than 20%. And obviously you can't reduce your other workload so you put in extra time to make your 20% project successful.

And for what its worth, I personally have never had a problem requesting for 20% time. Like all big companies, it really depends on your team and boss. I believe your experience of straight out rejection is more the exception than the rule.