SAN FRANCISCO, United States (AFP) — WhatsApp co-founder Jan Koum on Monday put out the word that he is leaving Facebook, which bought the smartphone messaging service four years ago for $19 billion. Koum said in a post on his Facebook page that he is taking time off to pursue interests such as collecting air-cooled Porsches, working on cars and playing ultimate Frisbee. US media reports indicated that a disagreement with Facebook over the privacy […]