Wall Street JournalWhatsApp Co-Founder's 'Rest and Vest' Reward From Facebook: $450 MillionWall Street JournalAfter WhatsApp co-founder Jan Koum announced he was leaving Facebook Inc. FB 0.59% in late April, he has continued showing up at least monthly at the social-media giant's headquarters in Menlo Park, Calif. His incentive for making the appearances: ...and more »