The unique advantage of DDG is its privacy. If FB were to buy it, most/all DDG users would flock elsewhere, so what would e the point?
Facebook can only grow ad revenue by purchasing it's competitors[who ironically swore to never be Facebook] now. WhatsApp has a large pile of users to make money from before they jump ship after Facebook is done alienating them all.
NOOOOOOO. Me and my friends switched away from WhatsApp just because Facebook bought it!