I mentioned this in another, similar thread several years back, but the one that I think drives me craziest, and I see it all the time, is "discrete" when what the writer, by context, means is "discreet." To quote Harlan Ellison, "'Aaaarrrgh,' I aaaarrrghed." (Confession: I may not have spelled "Aaaarrrgh" quite the way Ellison did; I don't have the source for reference.)
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Big Brother is watching you. And damn, you are so bloody BORING.
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Big Brother is watching you. And damn, you are so bloody BORING.