You use [sic] when quoting somebody to indicate that they have made an error, and in quoting them you have not made a typo but are faithfully preserving that error in your quote. Thomas Jefferson, writing the first draft of the Declaration of Independence in a drunken stupor, scrawled "All men is [sic] created equal." OK? It is an editing mark. It is NOT used when you are unsure of the spelling of a word and just decide to tack it on instead of looking up the correct spelling. This drives me especially batty because it's one of those errors people make when they're trying to use a word or phrase that they don't really understand. Same with "for all intensive [sic] purposes" (shudder). It's a valiant attempt to make yourself look smart, but it has quite the opposite effect. So no more saying "Hey guys I think Arnold Shwarzelneger [sic] is a good actor!" unless you're quoting someone and pointing out his error, m'kay? M'kay.