Even changing IP probably isn't enough, though. First of all, your computer sends out all sorts of information when you make an http request (or any TCP connection). It's not really my area, and I don't want to say anything untrue, so look it up yourself, but your machine can probably be identified by that information alone.

And even if not, if you provide enough search requests, and that information is coupled with limited IP data, sophisticated data mining algorithms can probably pick out your behaviour. That's a lot of effort, though.

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"It's turtles all the way down."