Mark Zuckerberg is a popular guy, and people want to be near him (probably to catch the cash falling from his pockets.) One housing developer caught on to this, and tried to build a mansion near Zuckerberg's home in Palo Alto with the added incentive that it was close to the Facebook CEO. But Zuck beat him to the punch.
Zuck has reportedly bought the four houses that surround his home in order to stop the developer from capitalizing on building a mansion next to him. The homes are located next door and behind his house, and the Facebook CEO is, in turn, leasing the homes back to their current owners. Essentially, he just became a landlord. The dude is worth $19 billion, so it isn't too crazy to think that he'd spend a measly $30 million to keep some privacy.
Kanye, take notes.
This will probably be good practice for him since he is currently in the process of building an entire Facebook town for workers.