Hmm, I somewhat disagree. Private information is anything you don't want public. By protocol, it isn't strictly private. But a phone number is private/unknown until its known, which is how most of us prefer it.

For example, in implicit social code it is impolite to give away a friend's phone number without asking them first.

The gray area for that is sharing a business phone number of your friend that they share widely through business cards or their website. Though typically it ends up being an email introduction if you really care to connect someone with your friend.

Seriously? Ever heard of whitepages.com?

I don't think whitepages has every name and phone number ever created

neither does snapchat

Yeah, but snapchat isn't suppose to give your number out.

Disagree. I suspect they would fall under personal data in the European Union under the Data Protection Directive.

indeed. rmc is right.

it's not that - resolving who people are across many services needs lots of fields of info. The more the better the accuracy of the algorithms that find the correlations.