First of all, I hope they succeed.
Wikipedia is one of a kind, at this point, we have no real competitors in the field of free wiki encylopedias, and having another out there could do us a lot of good. Having another group out there doing what we do, but better in some ways (inevitably) would spur us on to improvement, unstick us from whatever policies and habits we might have which are producing suboptimal results, and I'm all for this.
However, in looking at their website, I think they're in for some major trouble.
First of all, the bitter anti-wikipedia attitude is rather over the top. Nearly every single page on Citizendium contains attacks on us. This is not an exaggeration. Look at the top of any of their pages, and you see "The world needs a better free encyclopedia". Better than what? Better than Wikipedia, of course. Not to mention their policy pages and statements and discussions, which are all about how much better they're going to be than we are, how they'll do right every terrible thing we do wrong.
Secondly, their claims that they're going to be able to avoid vandalism, and avoid something like the Essjay situation happening to them, are quite dubious.
They've already been extensively vandalized. Look at http://en.citizendium.org/wiki?title=Special:Contributions&target=Peter+... for a bit of amusement. 10% of their articles vandalized by one person, and it took an hour for anyone to notice it was happening! Had this vandal used a bot, instead of apparently doing it by hand, he could have gotten their entire 1000 article database.
Something like the Essjay situation is vastly MORE likely to happen on Citizendium. This is because Citizendium forces all editors to give a name and upload a bio, and it gives experts broad authority over articles on their area of expertise.
If you force everyone to give a name and enter a bio, you will get large numbers of fake names and fake bios. If you give experts the ability to automatically win every edit conflict in articles in their category, you give a strong incentive for people to fake credentials. Imagine how many cranks we have of various sorts who would love to be able to say, "Look at my credentials, I'm a particle physicist and a Doctor of Alienology, therefore my edits on [[Anti-gravity machine hidden in Area 51]] must stay".
That having been said, if they can stop driving away 3/4 of their potential editors with their real name policy, and start being Citizendium instead of Anti-Wikipedium, they may well manage to be a success, to rival us, and to force us to better to avoid losing many of our best editors to them.
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