Shona Brown, age 41, (photo at left) and Sheryl Sandberg, age 39, (photo at right) are two of the top female executives working at Google. As of today, Sandberg has left Google and gone to the competition. She's just become COO for Facebook.

Valleywag wrote recently that Sandberg can't stand Brown. Was this the reason she left Google? Most people leave their jobs if they don't like the work, don't like their boss or get a better paying offer. The middle option seems the only one likely here.

The two women are very different in their self-promotion activities. Sandberg has no qualms taking all the credit for the development of Google's advertising products. Brown, on the other hand, prefers the quiet backstage role of strategic leader. She doesn't go out promoting herself the way Sandberg has. There isn't even a Wikipedia entry about her.

It will be interesting to see how this story unfolds. It seems to be a huge coup for Facebook to get the inside scoop on Google.