But there is some degree of success mentioned in the article, even if it doesn't work for huge networks.
That being said, some degree of privacy is better than none at all. Currently Facebook et al upload every single piece of contact information we have on our devices. That's insane from a privacy perspective.
It's really not, though — see the comments below. There are current approaches which send on the order of magnitude as much data as in one party's address book.
