By leaving Facebook to play Frisbee, WhatsApp co-founder to lose $1 billion

Jan Koum’s exit from Facebook Inc. could prove costly. A speedy departure may prevent him from collecting as much as $1 billion in stock awards.

The chief executive officer of messaging unit WhatsApp confirmed in a Facebook post-Monday afternoon that he was leaving the company. The announcement comes before the final three vesting dates of restricted stock unit awards tied to Facebook’s $22 billion purchase of WhatsApp in 2014.

Koum, 42, got about 24.9 million restricted shares as part of the deal. The stock vests in increments until late 2018, with 1.9 million shares due to vest in mid-May and mid-August, plus a final tranche of 2.1 million set to be issued in November.

The awards are contingent on him still being employed through those dates. He would forfeit 5.8 million shares, worth $997.5 million as of Monday’s close, if he left before May 15, unless his exit is categorized as an involuntary termination or a good-reason resignation, regulatory filings show.