For those who have not tried it, separately Google your own name, your nickname, and your screename(s). Enclose your name or nickname in quotes if there are spaces between, e.g., "John A. Doe", or "Johnny Doe".
You may be very surprised at what is on the internet, and how long it is on there for (with archiving, its essentially forever).
I have heard uncorroborated stories of people "flaming" others on websites and forums only to have their messages come back to haunt them later in life.
P.S. I use the term "Google" in the generic sense; if your favorite search engine is Yahoo!, Ask, MSN Search, or something else, use your favorite.
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"When you have eliminated the impossible, whatever remains,
however improbable, must be the truth." Sir Arthur Conan Doyle