The Wikimedia Foundation has launched a prototype of a visual editor, to be used on Wikipedia, and as part of MediaWiki. You can check it out on the VisualEditor namespace on the MediaWiki site.
This is exciting, because their effort could make editing articles easier for more people. It was really depressing when I realized that nearly everyone I know is aware of Wikipedia, but has never edited it, or seen wikitext. In an amazing example of contextual privilege, I had just assumed that everyone made little edits to Wikipedia, or had wikae on their personal sites.
I’ve been playing around with LocalWiki for a while, in part because it focuses on two areas that are useful, a WYSIWYG interface and mapping. When I found out about this project I thought that it would be great for nearly all of my clients, because they all have members that can benefit from collective knowledge, especially geo-data.
It is difficult, though, because I am generally bothered by visual editors. When I install WordPress for folks (and I host over a dozen instances for my tribe), the first thing I advise is to turn off the visual editor. I equate it to speaking well, instead of good. You will be able to share your ideas, but you won’t fully understand how it is published, which is empowering in ways that most people won’t understand until it clicks.
My goal, then, is to encourage people to use sites that have a aggregate benefit, like a wiki, while also providing training in digital literacy.
It always goes back to digital literacy. 
Addendum (2012-06-23): Mark pointed me to a message that links to a test wiki where the editor uses EtherPad for collaborative editing. I’ve used the embedded EtherPad into MediaWiki for writing fiction with my peeps, so this is an interesting take on it. Further down the thread it was mentioned that someone is working on collaborative editing in the visual editor. Neat stuff!
