Mark Zuckerberg -- I Spent $100 Million ... Damn Straight, I'm Building This Wall (PHOTO)

Mark Zuckerberg's 6' stone wall around his $100 million Kauai property has blocked out the Pacific Ocean to neighbors ... some of whom are livid. The Facebook founder bought the 750-acre estate in 2014 and now wants to shore it up, but a 5'8"…