* The vast majority of the time, Wikipedia is a wonderful repository for an unimaginably huge quantity of human knowledge. Whatever else it does wrong, it's still better than anything that's come before - or practically anything else around today - probably by a few orders of magnitude (on whatever scale you care to measure its overall usefulness). It has several strengths - mainly, the use of collective knowledge over the singular knowledge (and commensurate opinions) of any one domain expert provides, in general, better coverage of the range of topics, better coverage of a given topic, and a dampening effect on opinions or unintentional bias, at least in topics not generally considered "controversial". Also, the fact that changes don't require approval by an editor greatly increases the volume of topics and edits that Wikipedia can handle.
* That said, there are places where it falters. There is always a small probability that the information you get will be incorrect, either because someone with insufficient expertise wrote it (or someone with sufficient expertise made a mistake), or because it's been intentionally (but not obviously) defaced. While such errors will generally be caught relatively quickly for prominent topics, for "second-tier" topics there is always the possibility of inaccuracy. This is shown by both the fake bio story (in which intentionally incorrect, and in fact rather libelous, information was left on the Wikipedia biography of a journalist for four months), and Eric Burns' Fort Kent experiment (search for "Fort Kent" - he inserted erroneous information into the entry of a somewhat small but not un-notable town in Maine, and it was not corrected after two weeks). How big of a problem this is tends to vary with the type of information you're seeking, but as it stands Wikipedia is a long, long way from being able to be considered a reliable, credible source of information in its own right. That said, I still use it for my day-to-day informational needs, but it is entirely insufficient should I ever need information for an "official" purpose. Perhaps the Wikipedia community is okay with this; I see it as a shortcoming.
* There is a problem of inclusion. Well, perhaps "problem" is too strong, but there are very definite subdomains of knowledge that people seem to think is not of broad enough importance to warrant inclusion in Wikipedia. (Yes, I'm talking about webcomics, but it applies to a lot of things - do we really need an entire page in Wikipedia for each of the nearly 400 types of Pokemon? The individual Pokemon pages themselves account for a little less than one in 2200 pages in Wikipedia, and the search results for Pokemon contain over 2100 pages - i.e. a little less than 1 in 400 pages in all of Wikipedia were deemed to have some relevance to the concept of "Pokemon". No, I'm not bitter about webcomics. Really.) And supposing we do end up with a set of subdomain-specific wikis, there's still the issue of coordinating between them so that they can represent one comprehensive body of knowledge. (Webcomics already has its subdomain wiki: Comixpedia. Incidentally, Scatterplot doesn't have an entry there, and I refuse to write it myself.) Anyway, if there are to be inclusion rules, they need to be consistently applied across all domains, and coordination with other domain-specific wikis needs to be made more effective, or else Wikipedia is going to appear biased towards focus on certain domains and ignorance of others.
Anyway. At some point, if I have the headspace (a term that I may or may not have coined, referring to capacity to think about or concentrate on something in between all the other crap that a busy person needs to deal with (maybe I did coin that use of the term, anyway - Wikipedia recognizes it only as a firearms term)), I intend to write out a model for editing processes for a collectively editable body of knowledge that I hope will address some of Wikipedia's weaknesses while preserving its strengths. I look forward to some good, quality discussion.
But now, I've already spent an hour on this, when I should have been working on Scatterplot.