IOD: Encouraging "Google Time" at Microsoft

You can't help but wonder what is actually accomplished during that 20% of time spent by each individual at google on a non-core job related activity.  Are these projects ever reviewed?  Have they ever led to anything you see? Or is it just a "coolness" factor and perk for working at a company now swimming in investor capitol?   When I was a test lead one of the biggest challenges was aligning peoples skills and interests with particular tasks so that they could feel successful. 

In the Developer Division we ask that everyone spend at least some time each month helping developers in the community. We try not to be too strict about specific time spent or what activities are endorsed. In recent reviews we've done of this practice it seems that the people that do participate end up spending anywhere from 1-2 days a month on their chooses community activities. Not quite 20% of their time, but maybe not yet enough to accomplish anything really spectacular on their own.  

This is just thinking out-loud, but I wonder what the response would be if we suggested this should be 20% of a persons time?  The time wouldn't have to be about helping customers directly per say, but their projects did have to be publicly detailed on their blogs or collaborative workspaces.