I hate having to deal with people by email.
Sadly, it's a big part of my job and also the only way I have to deal with some people. It's too easy to avoid answering emails you don't want to deal with. I know I'm guilty of it myself, but I do make an effort to at least give a token reply.
This is a public service announcement broadcast: if you really want to piss me off, ignore my emails. Especially if it's important. Even more so if it'll only take a yes or a no answer to send me on my merry way.
</sarcasm>