Spell-Checking "Obama" into "Osama":

Benjamin Zimmer (Language Log) reports on this, and a quick experiment confirmed it. (Of course, as ABC News points out, it's not that someone at Microsoft is somehow deliberately anti-Obama; it's just that Obama wasn't in the dictionary -- that makes sense -- but Osama was, so the spell-checker suggested it.)

As the ABC story puts it, "When Fast Isn't Fast Enough, Spell-Checker Isn't Always Your Friend."