I think that not following instructions is probably the worst... there are so many posts where people keep asking for basic info like the software, or media, or drivers ... and it's never provided.

I'm not sure that getting frustrated at miscommunication is very fair... especially with non English language speakers, as the miscommunication usually comes from both sides equally.
In fact, is often the most extreme between two English language natives who are from different countries and just fail to understand each others cultures too well...

The only time this gets on my nerves is when people use internet shortcuts - this is really a separate language and totally unfair to anyone who is not really familiar with English, or the shorthand being used... Plus no punctuation (ok, that's a personal annoyance of mine).
(where is deanimator????)