If I were Mark Zuckerberg...
Mark Zuckerberg is obviously a very rich man, in fact he is worth around 17.5 billion. To put that in perspective, if you had one billion dollars let alone 17, you could spend $1,000 a day for 2,739 years. So from that you can see that if Mark wanted to he could simply bestow his business upon another executive and be on his merry way. Yet that is not what this billionaire wants to do, in my opinion he is still longing for a better Facebook, which I admire him for.
In that case, here is what I would do if I was Mark Zuckerberg...
Currently if you search a term in your Facebook search bar, you will see related people, pages, and a bunch of Bing hits. That to me, is a place for Facebook to naturally grow.
If I were Mark Zuckerberg I would make a very gutsy move. I would take all of this useless cash my company has and dish out enough money to buy Bing. I think right now with Microsoft's push toward making their own hardware shows that Bing is not a top priority.
Now that I have my own search engine I can have the amazing ability to have people search anything in my search bar. Not only that but I can see what they are searching and use that to "fine tune" what ads I put on their page.
After I have that search engine I would tell some of my most talented web designer and developers to stop their work. I would say "Facebook if fine the way it is right now, and it can stay like this for a long time."
Then I would instruct then to crank out what I would call a Facebook browser. After that time of quiet development on my browser and putting the finishing touches on my search engine I would release my bundle to the world.
I would be able to have my own Facebook based browser, and my own search engine in the browser, all tightly knit together by the social network I had spent so much time creating in the previous years.
Then what would I do?