There are three active threads about this, the present one and these other two:
"WhatsApp is going to share your phone number with Facebook": https://news.ycombinator.com/item?id=12358751
"Looking ahead for WhatsApp": https://news.ycombinator.com/item?id=12358205
Normally we'd merge the threads, but the discussions are large and come from three different perspectives, so that might not be best. HN practice is to have one front-page thread at a time about a story, but if you're concerned about the topic you might want to check in on the other discussions.