Player Feedback
As soon as your game is online and people start playing it, they will start expressing their opinion, whether you ask them for it or not. Somewhat ironic is the fact that those who are smarter and stronger in the game will usually not post on the forums or send e-mails complaining about things or suggesting new features. There are, of course, exceptions from this rule, but if you watch any MMO forums you will notice that most of the suggestions are worthless.
The problem is, when someone complains about some aspect of the game, the complaint will be egocentric, focused on their particular problem, and not on the overall benefit of the game. For example, some players want certain items to be cheaper so that they can afford one, without thinking that making the item cheaper will cause in-game inflation.
My personal experience with asking for feedback from the entire community (such as an open forum post) is bitter. The majority of people will NOT even bother to read your post, they will just read the title then click on the "Reply" button. And even if they do read your post, they will still think about what benefits them, and not the game as a whole.

@Mihai B Dupa cum vezi, ma perfectionez (continuu) : daca nu iese intr-un termen, il marim. Daca nu iese nici asta, voi discuta la nivel de secole direct.