Comment by iamnothere

You don’t necessarily decide what to put online. Friends may upload photos of you, data brokers make your information available to “people search” websites, if you buy a house your information is available unless you put it in a blind trust, etc. If you go beyond the web to private services then you have companies like Flock and retailers who use facial recognition, who make their data available to subscribers and partners.

Disturbed people with access to this data can use it to harm people, like the Ebay exec who stalked a critic or the occasional police officer who stalks a romantic interest.