We've all made the occasional typing mistake in an email or text message, and usually the iPhone is great at catching these and changing anything close to the word into the proper spelling. This is a good thing... most of the time. Sometimes, it's quite disastrous.
If you mistyped a message to your sweety and your text to her came out as "you are such a sweaty!" she might not get the warm fuzzy feeling. Neither would she like a message saying you'd "like to die with her tonight," as opposed to "dine" with her.
These are a few examples of some iPhone text mistakes you can find at DAMN YOU AUTO CORRECT which has many hilarious mistakes for your reading pleasure. I bet you can't read much without laughing historically... I mean hysterically.
I've never done anything quite that bad on my iPhone yet, but I've had a few silly ones!