A few days ago Google announced a one-time raise of 10% for all employees and a $1,000 bonus. Well, "announced" in the sense of circulated an internal memo and then fired the guy that leaked it. Perhaps "didn't announce" would be more strictly accurate. But they did it, and the general consensus is that they did it to arrest the brain drain to Facebook.
This raise is estimated to cost Google one billion dollars. Then yesterday they offered one engineer $3.5 million to turn down a Facebook offer. So what does Mark Z have to do to bankrupt Google? Simply offer their engineers jobs, one at a time.
Google employs c23,000 people. It is apparently willing offer anything from half a million to three and a half million dollars to keep them. The company has $33.4bn. Perhaps Google really can operate with its engineers sitting on cash piles of a few million dollars each. But that cash pile can get whittled down pretty quickly if other tech companies are willing to keep offering Google's best guys paper and Google has to keep outbidding them. It's sure worth Facebook's time to hire a couple of recruiters and have them wander on to the Mountain View campus every couple of days and make some offers.