Why are people so willing to give away their personal information to complete strangers?
It's because humans want to share information. And in fact, they share information a lot more freely than other "things" such as goods and services.
Which of these are you most likely to provide without thinking much about it?
• To give a stranger directions to the bus stop (information). • To take a stranger to the bus stop (service). • To give a stranger bus fare (goods).
If you're like most people, you'll freely give directions, but you'll resist giving away your money.
And that's how civil human society works, we share, and we especially share information, because it costs us little and it helps society function to more efficiently.
This idea was expressed by Clay Shirky at Austin's South by Southwest (SXSW) in 2010. Shirky has given multiple TED Talks and is widely respected for his thoughts on technology's effects on society. If you're interested in the subject of privacy, you should really watch Shirky's 2008 Web 2.0 Expo NY presentation: It's Not Information Overload. It's Filter Failure.
During the presentation, Shirky makes the following observation: privacy is a way of managing information flow. According to Shirky, the big question we're facing about privacy revolves around the fact that we aren't moving from one engineered system to another with different characteristics… but that we're moving from an evolved system to an engineered system.
"Managing our privacy" isn't a natural act.
What maintained our privacy in the past was that it was generally inconvenient to spy on people. Platforms such as Facebook present a new and unique problem and new solutions (filters) are needed, rather than to retool old existing filters.