You can take them in several periods.

In Mark’s case, a long contiguous departure puts a lot on Sheryl Sandberg’s shoulders; she recently lost her husband and has children of her own, so that might not be ideal.

Internally, Mark’s work ethic is… known to be high, and less a model than the many other employees who become parents. Because employees tend to be Facebook-friends with everyone they know internally, you see a lot of baby-photo pictures: that has far more impact on your perception of what is explicitly told to be the right thing for the company, i.e. take all the time you need with your baby.

DOES it put a "lot on her shoulders"? Does it really? At a company as large as Facebook, is there ever really so much riding on any particular person in management? I doubt it.

I’m not familiar enough with the higher management, but yes, there are many incredible people to support both. I suspect that when it comes to dealing with parties like high-level political players, or being the public face of the company, they are unique. I'm noticing Lori Goler's name more in the press; that could be an effort to avoid that. Chris Cox, Boz, Shrep and Jay Parish are all people I wish people knew more about (outside of Hacker News; any regular here not knowing them is a clearly at a loss).