WhatsApp co-founder Jan Koum leaving Facebook over ad plans

Jan Koum, Facebook Inc. director and co-founder of its WhatsApp unit, is leaving the messaging service after what people familiar with the matter described as disagreement over putting advertising on its app and frustration over the confines of working in a big company.

Koum, who was chief executive of WhatsApp, gave no reason for leaving in a Facebook post on Monday about his departure. The move follows the departure last year of fellow WhatsApp co-founder Brian Acton, who has since been publicly critical of the social-media giant. The two men, both privacy advocates who started their encrypted messaging app nearly a decade ago, joined Facebook   after it acquired WhatsApp in 2014 for $22 billion, making them both billionaires.

Koum’s departure followed an internal debate over whether to put advertising in WhatsApp, a move that Koum opposed, as did Acton, according to a person familiar with the matter.

WhatsApp is free to users and has long eschewed advertising — the main source of Facebook’s business — leaving it with little or no revenue. But in coming months, Facebook has discussed plans to introduce ads to its “Status” feature, which allows users to post images and videos that disappear within 24 hours, much like on Instagram or Snap Inc.’s   Snapchat, the person said.

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