Like it or not, the types of questions you see allowed or discouraged on SO are in large part the result of years of discussion, debate, and collaborative moderation by a rather large portion of the userbase on SO. Even the handful of people able to take unilateral action to include or exclude questions are elected - hence the event that instigated this thread to begin with.

Ultimately, the folks with the most power over these decisions are the ones using the site. If you don't like what's being closed, cast your re-open votes and convince others to do likewise.

That particular question ended up being closed and reopened multiple times, and discussed heavily on meta. Ultimately, it reached the point where it was simply unmaintainable, in spite of the hard work of many people involved. So it was locked to preserve it.

If you visit some of the more well-maintained tag wikis, you'll notice they contain sections for freely-available books amid links to other useful learning resources. This tends to keep them smaller, easier to maintain, and much more likely to be maintained by folks who know something about the topic. Example:

http://stackoverflow.com/tags/php/info