WhatsApp CEO Jan Koum said on a Facebook post Tuesday that the service now has more than 700 million active monthly users, up from 450 million when Facebook Inc. announced its intention to purchase the mobile-messaging-app company last February. "Additionally, every day our users now send over 30 billion messages," Koum said in his social media entry. Facebook's cash-and stock deal to purchase WhatsApp was worth about $21.9 billion US when it closed in October, up from the $19 billion US it was announced earlier in the year as a result of gains in the value of Facebook stock....