I have created a wiki (I choose not to link for a number of reasons) and been a healthy contributor on quite a few. You might notice that almost every wiki has a copyright license at the bottom of the first page. This license will tell you what happens with the stuff you add to a wiki. For instance can others edit your additions, can people take your additions and bring it to another place (not on that wiki), can your addition be related to any commercial use, and realistically the most important, IMHO, what happens when your article is edited.
There are many "commons" licenses that allow for an almost public-domain-like allowance for the copyright material. Usually any kind of personal use is allowed. However, the differences can be suffocating.
Recently my all time favorite game, Guild Wars, started an official wiki. This was awesome except that awesomeness was tempered by the fact that there was already a goliath-size unofficial wiki in existence. For the rest of the article I will call the former "OGW" (official guild wiki) and the latter "GGW" (goliath guild wiki).
The community was pretty excited because the benefits of having an official wiki were pretty substantial: (a) the owner would not randomly decide to take the wiki down, (b) the hardware and connection could be substantially improved, (c) developers and personnel of ArenaNet might be persuaded to add to the wiki, etc.
Community: Ok, well let's just copy everything from the very substantial, nearly complete GGW to the new and blossoming OGW.
ArenaNet: We can't do that.
It seemed that the license on the GGW did not allow for any commercial use. OGW, owned by the company that ran Guild Wars, would definitely be used for commercial use even if only "lay people" would be adding content.
This was horrible. Two wikis on the exact same subject create the biggest bane to a wiki's existence. Competing wikis are about as stupid as competing operating systems, as entertaining as it may be. Ok, bad analogy and wrong battleground.
Anyway LDRAW (Lego CAD development) recently had nearly the same problem shifting their parts library over to a "commons" copyright license. This took nearly a year because they had to contact each parts author and ask that author to release his copyright to the part under the new license. The authors that could not be contacted had their parts deleted off the LDRAW server, and those parts had to be later remade in an original manner.
This solution would be perfect for GGW and allow the OGW to replace it. The problem is that a wiki is editable by practically anybody. Many people create usernames to attach to their wiki additions/edits, but just as many edit anonymously. Well not totally anonymously because IP's will be tracked, but still contacting an author based on their IP is not very feasible. The other problem is that so many authors add their stock to the wiki article's soup.
Sure Bob the Farmer may have started the wiki article on sheep, and then Sally edits his article for grammar and had to add a sentence on sheep diets, Gregor added a paragraph on sheep diseases, ph3@r added a bit on having sex with sheep, etc. As of the current iteration, let's say, 80 authors have put their hand on the sheep wiki article.
Can our law really handle the copyright problems imposed when 80 people add material and then walk away? Most people that use wikis know that nothing is sacred. What one might feel is sacrosanct is just another factoid to another, and may edit out the feelings of holiness to make it more neutral. People also get their facts wrong, add opinions, and even make stuff up.
What about the fact that the author's copyrighted material is basically in the hands of another person? If the server is taken down with no backups, etc. the material may be lost forever. Should that matter? Should copyright really protect all the crap that is shoved out onto the net each day (including this article) to the degree that a book or manuscript is protected?
Now American intellectual property law is based on the notion that you must protect your rights. So while 80 people might hold some iteration of a copyright on the sheep article, it is probable that no one will actively seek to protect their copyright. Still, companies wishing to make things "official" will not wish to take on the boatload of liability.
I feel that this is another stab at how archaic and stupid our copyright laws are. We are coming upon another Mickey Mouse cycle for copyright. I hope our Congressmen attempt to learn about copyrights with a forward-looking expansive scope, instead of to just a commercial degree.