These
entertaining and
informative writeups really do convey what it means to be sarcastic; It's true, there was
no way to express sarcasm in
writing before the
Internet existed.
(/sarcasm)
The thing about sarcasm is that it's at its best when it's subtle. Personally, I think that the "(sarcasm)(/sarcasm)" bit spoils the effect- It's a bit like telling someone "This is a joke.." before telling them one of those jokes which you're supposed to tell as if it's a serious story.
So I prefer to just add the ending (/sarcasm) bit, in case the reader missed the subtlety... :)