Okay, I hate email conversations. It sucks. I never read the messages right, and when I talk to the person later they're always like, "Oh, I didn't mean it that way." Although, it can be fairly illuminating, what people say when you're misunderstanding them. And it's not just email, it's IM messages as well.
There's just way too much that I say with my face and voice for me to be able to communicate effectively with simple printed words. Maybe in writing letters there's enough time to put thought into how this is going to sound on the other end, but with semi-instant, back and forth messages, there's too much that gets overlooked.
I think my most common mistake is reading too much into it. I mean, it is fairly rapid, but the problem is that the words sit there and stare at you for ages. They're words that are typed out without thinking, immediate response kind of stuff, words that in the best situations are uttered and forgotten, moved past, and are only brought back in half-remembrances.
But with instant messages, they're immortalized, or well, at least they are until you close the window. So you have time to go back and rehash exact phrases. Time to sit and stew and ponder, "What did they mean by that?" And with email, you can bring it back days later.
As I said before, it sucks.