This "expression of ideas" thing is going to get a bit repetitive, isn't it? I suppose that's the point.
I was thinking over the flaws in Wikipedia yesterday: it can sometimes be inaccurate. I tried to figure out a possible solution, and, of course, I had to start at the root of the problem.
The root of the problem is that anyone can edit Wikipedia. This is great for making content - having so many editors can be an extremely good thing. However, since anyone can post content, anyone can post inaccurate content, and thus problems arise.
I think part of the problem is a lack of organization. In a traditional encyclopedia, there would be writers, editors, and several other people who work on a single page, all before it is printed. In Wikipedia, there is no delay between when someone edits, and when it goes live - it just does.
I think that Wikipedia should work more like open source software, which also (sometimes) allows anyone to edit. The "live" version of a specific page should not change every day, or several times a day. Instead, it should change every month, or every few months. Before going live, it should be reviewed for accuracy and edited for grammar, organizational, and spelling errors.
There should be two other versions (besides the "live" version): the development version, and the review version. The development version is the version anyone can edit (like Wikipedia). The review version is one which is only for review and editing, and is not to be edited any further with additional information (and, perhaps, can only be edited by reviewers).
This system would keep the benefits of an encyclopedia written by the people, but also keep data accurate.
Discussion
Another area which is lacking in Wikipedia is that of discussion. Though there is a "discussion" page for every page in Wikipedia, this is nowhere near integrated enough. People should be able to highlight a letter, word, or phrase and comment on it (and reply to such comments). Editors would then be much more able to tell what could be wrong with the page than they can in the current system, which would require them to go back and forth between the discussion page and the page itself.