The Knights of the MMO Table have a discussion about crafting in MMOs going on. Check the articles from Nerfbat, AggroMe and Moorgard. Some points from them:

“Adventuring and crafting are competing styles of play. I say this not only because a player must generally choose which they will do at any given time (yes, sometimes you can adventure to acquire things for crafting or craft to further your adventuring, but you understand what I mean), but because they are often pitted against each other by the very design of certain types of MMOs.” (Moorgard)

“The summary is that certain types of games can support deep crafting systems. Games that are both adventure-centric and item-centric will usually do well to avoid complex crafting systems, because you are either going to be slighting your adventurers by making crafted items great or will be alienating all the crafters completely by making a complex system that is not worth their time.” (Nerfbat)

“I can go on the net and in a few minutes find cheaply made flash games which are more fun then crafting. So why not dedicate some time to making the process of crafting addictive and fun? Whether you want to include elements of twitch play, turn-based strategy or real time strategy, the key is to make things interactive and require player skill. Just take a look at my harvesting examples and apply them to crafting. Memory, reflex, sound recognition, spatial visualization, puzzle solving and strategy are just some of many elements that could make crafting a game and not a chore. Of course, you do not want to completely remove players from the world. You do not want to have them sit down at the forge and then Tetris pops up. But working great gameplay into the theme and feel of the world is merely a challenge and not a barrier.” (AggroMe)