And if billions of people trust Facebook, that's just a sad commentary on the amound of critical thinking in the world.
And also, did you just call the gizmodo article "fake news"? It this [0] then also fake news to you? Seems to me you are getting your true news fix from a news feed somewhere.
[0] https://www.wsj.com/articles/facebooks-onavo-gives-social-me...
They are touting the VPN as being protection, when in actuality they are using it to gather data on the users that use the VPN.
I do not understand your comments in light of these facts. If one trusts Facebook, then using Onavo isn't a concern for them, but they should be aware just because it's a VPN it doesn't imply any kind of privacy or protection, and should be aware that Facebook's marketing/use of Onavo is shady.
If one already does not trust Facebook, then it should be clear to stay away from Onavo, whether found randomly, through an app store, or advertised by Facebook.
I think you are confused. "Used" and "trusted" mean very different things, and you seem to be using the latter where only the former is justifiable.