Researchers claim 'largest leak ever' after uncovering WhatsApp enumeration flaw

This doesn't seem like much of a leak. It sounds like users created public profiles that would be shown to anyone who entered their phone number while searching for other users. The researchers managed to get a list of users and the public information in their profile by looking up random numbers, but all they got was the public information users put in their profiles.

Since facebook didn't rate limit the researchers (or anyone else) it allowed them to collect a big dataset of publicly avilable information, so shame on facebook (as if they had any), but it's not like people's secret/private data was exposed. Nobody should be upset that the photo they uploaded and put on the internet as their public profile picture gets seen by somebody else. People who don't want their "sexual orientation, political views, drug use" or whatever known shouldn't put that in their profile where anyone and everyone can see it.