Is Facebook’s latest talent grab part of a much bigger story?

Paul Adams, the Google UX (User Experience) researcher, who pointed out some flaws on Facebook this year, has now left Google to join Facebook.
Whilst Adams is clearly a very bright guy, I believe this move is potentially an indicator of a MUCH bigger story, regarding the balance of power with these 2 Internet giants.
Power shift?
Until recently, the idea of anyone leaving Google for a competitor would have been unthinkable. For years, Google has been regarded as THE place to work, for anyone seeking a career in the industry. I believe it is telling that such a talented Googler has joined Facebook. It’s also interesting that following Adams’ critique, Mark Zuckerberg and his team looked for what they could learn, rather than take it as some kind of attack.
For those who missed it, amongst other observations, Adams’ critique focused on the need for Groups, stating that people interact very differently with different people. It’s alleged this was what prompted Facebook to go into “lock-down” in the summer, to create Facebook Groups. Clearly, Zuckerberg saw the value in what Adams was saying and offered him a job, which Adams accepted.
With Facebook’s increasing reach and influence, I’m wondering if Google will find it increasingly hard to attract and retain the industry’s top talent?