A Canadian judge recently ruled that police did not need a warrant to request the information on an Internet subscriber from an ISP based on their IP address. The judge said that one's actions on the Internet have no expectation of privacy.
Most people I know would be very unnerved to think their behaviour online is somehow public data, or that their surfing habits could be linked back to them with a simple unwarranted request. While the case in question was one of child pornography for which many would feel this action was justified, the judge's ruling did not take this into any consideration as far as I noticed and as such this warrantless personal data request may be repeated for any type of online investigation. I am not a lawyer mind you.
Some people have been asking what the difference is between an IP address and a physical address. Everyone should expect their phone number or address will lead back to their personal information via a simple reverse directory of course. As I said on a discussion about this story on Slashdot though,
One of the primary differences is that IP addresses are left behind as cookie crumbs everywhere you go online. In real life, you wouldn't leave your home address and telephone number on business cards laying on the street at every intersection with a date/time stamp indicating that you'd been there, would you?
While the type of information seems similar, the resulting availability of personal behaviour data that is discoverable as a result is unnerving.
While I feel that most peoples' behaviour on the Internet is reckless an that people should take their personal information more seriously (by using encryption on E-mails, anonymizing proxy servers, etc.), I think the very fact that people do not take this seriously is proof that there is, contrary to this judge's opinion, an expectation of privacy online, however unwarranted.