Autocomplete is a bugbear of mine, since it's the fastest way to type on a touch keyboard and people have a bad habit of not proof reading stuff that they are sending.
It seems that at least every few days I get an Email like this.
Well, that is certainly one of the main problems with it. For me it comes down to the edge cases. My Apple password contains letters, numbers and special characters. It takes me about a minute to type it on the iPhone. If you have to rely on auto complete for edge cases, then you can never accomplish more than the most shallow content creation, such as sexting or 5 word emails.
It seems that at least every few days I get an Email like this.
Subject: Very Important!
< Incomprehensible >
Sent from my iPhone