Nice graph from the FirstRain research service showing employee turnover trends at Google and Yahoo over the last year. Red denotes turnover-related losses, and green denotes gains. While both companies have seen losses, the level at Yahoo -- especially in recent weeks -- is daunting.
Just by way of comparison, I have also included the recently-deceased Bear Stearns, whose losses pale against Yahoo's executive exodus.
Update: If you're thinking of leaving Yahoo, there is now a boilerplate resignation-letter generation tool out there. Check it here.