When Marissa Mayer left Google last year to become Yahoo's CEO, she took more than a decade of experience with her. One thing she didn't take was Google's practice of giving its employees what amounted to one day a week to work on personal projects on company time. Google sign (Creative Commons)Once perceived as a smart, even revolutionary, way to keep employees engaged, the "20-percent time" approach appears all but dead at the Googleplex, with observers wondering whether it did the company any good and one prominent analyst describing it as "screwy." "I'm not aware of any other company that did this," said Rob Enderle, Principal Analyst at the Enderle Group in San Jose. "It was kind of a screwy idea, very unstructured, and generally engineers don't deal well with 'unstructured.'" Kevin Surace, a serial entrepreneur and a former Inc. Magazine CEO of the Year, wonders what value the personal time actually brought to Google. While some credit Gmail, social media and other projects to "20 percent time," Surace says even such successes have had little actual impact on the company's business. "In the end, [more than 90 percent of] revenue still comes from Adwords and search, which it did 10 years ago. So all these other projects, while interesting, didn't move the needle," said Surace, now CEO of Appvance Inc., a San Jose developer of application testing products. While Surace did say the free time probably succeeded in attracting engineers who otherwise would not have gone to work at the company, "Microsoft looks at it and laughs." Redmond, he observed, believes its engineers are substantially more productive than Google's. As for Mayer and Yahoo, "Marissa didn't even attempt such a thing. She went the other direction, in fact. Why? What does she know that we don't?" Surace wondered. On the other hand, Analyst Rob Enderle said it's good for companies, including Google, to "try something new out once in a while." "To their credit, I think they realized that the idea sounded better than it actually turned out to be and switched to a more traditional process." Surace believes that in retrospect, "the real question is if Google had not done it, what would the impact to top line and bottom line be today?" Another analysis, this one from the employee perspective, is offered by Visible Energy CEO Marco Graziano, who says, "Something is wrong when a smart engineer spends 20 percent of the time doing something he likes and 80 percent what he is told to do. It should be the other way around." And that, according to Graziano, is "why at some point you start your own company." Then 20-percent time becomes 100-percent time. Is everyone at Google always doing what they want to do? With the other perks and benefits the company offers, it's open to question whether many employees notice -- or even care -- that 20-percent time seems over.