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In Pictures: Can your IP address give away your id...
Doe knows YouTube
Now Doe knows that this person is in Mountain View, Calif., and works for YouTube, a Google-owned subsidiary. If Doe knows anyone in the Mountain View area who works for YouTube, he has likely found the culprit. If Doe doesn't know anyone, he can call YouTube and provide them with the time, date, URL, and message and then ask them to check their logs for the name of the individual.
In Pictures: Can your IP address give away your identity?