An interesting article In NBC News in there Technology section:
Bits of you are all over the Internet. If you’ve signed into Google and searched, saved a file in your Dropbox folder, made a phone call using Skype, or just woken up in the morning and checked your email, you’re leaving a trail of digital crumbs. People who have access to this information — companies powering your emails and Web searches, advertisers who are strategically directing ads at you — can build a picture of who you are, what you like, and what you will probably do next. Revelations about government counter-terrorism programs such as PRISM indicate that federal agents and other operatives may use this data, too.
“Google knows what kinds of porn everyone in the world likes,” Bruce Schneier, a security and cryptography expert told NBC News. Not only are companies tracking what you are doing, they are correlating it, he said.
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