Whats the most irritating?
To me there are a couple.
First: people (affialate programs and other webmasters) that don't answer emails, answerring an email should be as normal as can be. It has nothing to do with time, there is always time to answer a question or something else.
Second: Scammers, there are a shitload of scammers here so you can never really trust someone.
And offcourse: the russians!
and a shitload more, but I still love it