Strongly disagree paintballer.
First, you can only set 5 trades, this is a big limit to start with.
Then you might want to trade something but not put it in a trade for display.
It is not possible to reverse sell either: I want to get rid of some monsters I know some people are looking for but I can't look them up: you can only see people offering what you want, you can't see people who want what you have to offer.
That is a feature that would add a lot to the game actually:
a "passive" wish list of (at least) 30 monsters, when selling, you can see the list of people who have the monster you have in their wish list.
As far as the trades on the message board are concerned, I find it pretty useless unless you have a large amount of time to waste strolling through dozens of pages of topics: no search function and the list of topics is so short, a topic gets bumped to 6th page within minutes.
Trading on MP is hard work, way too hard work.
Also would be good to be able to trade gold !