WW:

Read some years ago, when Facebook and MySpace were about even for use, that MySpace was owned by Rupert Murdoch's News Corp.

Part of the "click here to get started" agreement (that South Park so perfectly spoofed) is that using MySpace gave News Corp permission to scan everything you posted.

Why?

It was a way to look for recurring words, specifically, products and popular media/entertainers. In short, it is a market-research tool. Billions of people would be chattering away about what they liked, or wanted to do.

This information, in turn, was sold to interested parties. Because they know in advance what is popular, and what is not, they can produce and price accordingly, to make maximum profit.

I believe FaceBook is the same. Why else would someone so magnanimously provide this 'free' service, investing millions/billions in servers and other internet hardware? Why would such 'Social Networking' sites be sold for hundreds of millions of dollars?