I'm not pointing out anyone's flaws - I'm having fun with it, because he was tired when he did it - it was a typo.
I see people writing "should of" instead of "should have" all the time on forums. It drives me crazy, but I never call them on it. I mentioned it here, so I could get it off my chest without slamming someone specific.
Think about it this way, though. If you see someone consistently making easy spelling and grammar mistakes, doesn't it paint a negative picture of that person's intelligence? I'm not talking about typos here; I'm talking about things that no one with a 3rd grade education should get wrong. I'm not talking about the OP here, because he says he misspelled the word by accident, because he was tired. That's understandable.
But when people who consistently misspell or use incorrect grammar get into the real world, the business world, they will be really embarrassed by the way their peers view them.