I place the blame squarely on Nexon's shoulders
Even if the volunteers picked were unsuitable for their positions, and did their job poorly or broke NDA, it is ultimately Nexon's fault for not selecting them correctly. I refuse to believe that in the entire community there cannot be found a few dozen people who are capable, responsible, and willing to work to help the game.
With the MWLB, as I said, Nexon failed to properly motivate the volunteers to continue working.
With the MLC, from what I saw, Nexon largely ignored all their suggestions, or at best took from them what looked like it would make money (Oz in Marvel), completely ignoring the spirit of the resolution.
In both cases, Nexon did not allocate resources to interacting with the volunteers and using their contribution. It's not too terribly surprising that people lost their drive, and eventually one (or more) got upset enough to break NDA. (Should not happen, of course, even when frustrated. But see previous paragraph about choosing the right people).
Also, not every attempt fails. The Volunteer Forum Moderator position seems to be working out well, for the most part. I believe this is because Nexon has no choice (they certainly aren't going to hire paid moderators, and the CM is overworked as it is), so they are willing to put in some effort to make it work. But with "mini-GMs" or a "game design advisory council" - well, they already have paid people doing that work, kind of. Higher management doesn't really understand what the player volunteers contribute that makes it worth the extra hassle to interface with them.
How does Nexon manage to find trustworthy employees, then?
How do they manage to find mostly trustworthy VFMs - and get rid of the bad apples without abolishing the entire program?
The people picked for the test server were completely random, so of course there would be plenty of useless or just plain malicious ones there.
But the MWLB and MLC were supposedly hand-picked after a lengthy process, and were still rendered useless and (a few) eventually driven to corruption (or simple carelessness).

Oct
MapleStory World/Server Transfer Event Thoughts
Yes, I'm back, welcome to maplestory2-mesos again, you know, some MapelStory players are confued now, they don't know whether they should move to another ms server, if they friends choose to stay.

Nov
Can Always Find Botters in MapleStory
Welcome to maplestory2-mesos, my dear friends, how's the day going? And have you played MapleStory today? Alright, get back on track, we are going to discuss the botters in game, which is always a cancer to most of normal players, you know, botters are really different with us.

Aug
Could We See A Better MapleStory Game In Future?
As an old ms player, I want to say that Maplestory concept have lost through time, I can't find more fun and excitement in this 2D side-scrolling game. And I think what has Nexon done to this game is not always the good things. I am hesitating whether should I recommand MapleStory to my friends.

May
Dissatisfied with Nexon's performance
I've been meaning to write this for some time now, but I've restrained myself from doing so out of my belief that Nexon would fix itself before June.

Sep
MapleStory Mesos and Equipment Drop Rate
I find it very hard to get enough mesos to upgrade my skills (Mastery Books) and Star Force (equipment) by just grinding nowadays.

Jun
New maplestory Class Suggestion Friendstory Lotus
When you play Lotus from friendstory, you are an alternate-universe version Lotus who gets lost in Maplestory World. The reason you got to mapleworld was uncertain.