There is definitely something wrong with trade chat. It isn't used the way it's supposed to. Or rather, it is over used the way it's supposed to.
I have most of my chars on a relatively small server and so trade chat is generally a not so crowded place, and you can mostly get your message through without too much trouble. Having played some on a really big server however, I quickly realize the flaws of the trade chat, and the ways it's being used.
Don't get me wrong, I don't belong to the clique of purifists who think trade chat is solely for trade, or the bunch of rp'ers who think you need to accompany each desire to trade with the story of your life. I do think trade could be used for other things than trade, even completely out of the blue things. -Even- the dirge (and other meme) things occasionally. After all, WoW is a game made up of it's community and will always be about what the community desires. I do not desire to prohibit this.
The problem isn't so much what people say in trade, but how they do it. On bigger servers I noticed, people spam. Really spam. If they want something, they don't post it once or twice or five times within a minute, but maybe 30 times, without exaggerating too much. Often with way too many exlamation marks and caps like there was no tomorrow. Why is this a problem? Because if everyone does this, no one will ever get their message through.
I've got a friend who told me he used to sit and wait until the perfect opportunity opened up in the trade, a short respite from all the spamminess. If you posted exactly then you could be lucky enough to be noticed by some people. That is unless alot of other people had the exact same thought and posted at that same moment.
I asked for a mage to portal me to dalaran, and a half second later my request was gone. Rolled away by people who were looking for raids, looking for people to raids, looking for crafters, offering crafts and everything else people use trade for. If they have to spam to be noticed they will, and then they have to spam to be noticed. See the evil cycle of doom here?
I've of course thought up what has to be the perfect solution to this however. Just give posting in trade a cooldown. Say you can only post once every 30 seconds or 1 minute. This would also greatly limit all the trollers out there, those who seem to play WoW mainly as if it was their personal msn or something.