20% time and individual project ownership at Google X have helped to make Google a famous employer, but I do get the sense that the drawbacks are becoming more visible as the company grows and people move on.

Some of this is undoubtedly belt-tightening, but it's a lot easier to ax a specific project when it had a few fervent advocates who are no longer around. I'd be surprised if this wasn't a factor in the high project churn Google is known for.