Well, it appears Wikipedia does not think the same way we do on this matter. The online encyclopedia powered by user contributions has begun cracking down and removing articles on MUDs, citing inability to provide verification along with reliable sources. Currently on the chopping block is the entry for Threshold, one of the oldest MUDs still active to this day. This isn't the first time Wikipedia has put online games under fire -- already pulling out the entries for BYOND, LegendMUD, and even removing the article on dragon kill points (DKP) for a time. The removal for the entry of LegendMUD is particularly painful, as there are other articles on Wikipedia that reference the LegendMUD entry, yet are still apparently viable on their own.
What makes this whole discussion so frustrating lies in how the MUD community has preserved their own history. Many of the facts and tales of the games comes through something akin to the oral tradition -- many users who have written about, blogged, or related their thoughts to others via community sites. Because of this, there is no main verifiable source to connect these MUDs with. Without a verifiable source, one of the main tenets of Wikipedia, all of these articles can come under fire. With the MUD community in decline, many of the older articles can't even be linked to or referenced -- providing only more problems with keeping these entries in the system.
Richard Bartle, Raph Koster, and Scott "Lum the Mad" Jennings have been discussing this problem on their respectful blogs and all three seem to be coming to similar conclusions. While the history of MUDs seems to be sinking into the ground, the Wikipedia article entries that concern themselves seem to be entirely off base and yet are more welcomed than the MUD pages. Bartle's entry spends more time on how much he dislikes World of Warcraft rather than his influence in the early MUD world and his career as a teacher of game theory. Raph's entry is more of a stub that reads like his resume rather than an substantial entry. Scott's entry is a long novel about his blogging and what he's been doing for the last couple years, and even he thinks it looks silly when compared to Raph's poor entry. Last, but not least, Rob Pardo's entry spends more time on how much he hates paladins rather than his work with World of Warcraft.
So while things like My Little Pony remain quite welcome in the Wikipedia universe, MUDs apparently don't. As Damion Schubert from Zen of Design has said, "Wikipedia is what it is." It's not perfect, it's certainly not 100% verifiable, and we may not agree with everything that's being done with it, but it's going to be that way. While it could be a great resource for MUDs, the old "use Wikipedia at your own risk" addage will always apply.
Update: Wikipedia deleted the Threshold article on January 7th. The final vote for deletion was 18 for deletion and 22 to keep the article in Wikipedia. Even with the majority on the side of keeping the entry, the article was removed from Wikipedia's database anyway. The final result was determined due to "lack of verifiable resources" and "little notability about the game," in spite of Raph, Scott, and Richard speaking up for the game and the precedent this may set for the other MUD entries on Wikipedia.