My understanding of the policy is that questions that are too subjective should be closed but not deleted, because they might still contain useful information for people.
So why was this question deleted?
The mods posting here have well-linked answers, but unfortunately, they don't actually answer the question... even the mod to "blame" (for lack of a better word) can't really provide an answer.
The truth is that it was deleted because it was closed. In time, that happens to most or all question that get closed.
It was closed because there was, and still is, a difference between what the community considers a good, constructive question and what the moderators consider a good, constructive question.
The question was closed by one mod, reopened by 5 users, and closed again by one mod. That decision is not likely to change.
Clearly, what your take away should be is that it doesn't matter if the community thought the question was helpful, informative or constructive.
It doesn't matter if new, upcoming, devs that work with you fervently apply one-return per function, or write O(n^3) functions when O(n) exists because
premature optimization is the root of all evil... or any of the other pieces of solid wisdom that potentially hundreds of users thought was important enough to upvote and then re-open. It's gone now, go figure out how to be a professional developer somewhere else. This is not the place for those kinds of things. "Not constructive" or "Too much like a list" they'll tell you.
I also hope you didn't get any reputation from that question - or think that reputation matters - because it's gone now.
As Thomas already mentioned, there is no policy in keeping around closed questions indefinitely. If a question was closed, it's on a path to deletion, regardless of the specific close reason.
We allow for a fair amount of time for the community to step up and salvage the question, for this specific question a little less than three months. The question was closed on Nov 20 '11 at 17:22 and deleted on Feb 9 at 17:01, and although there were edits in between, none addressed its "non constructive" issues significantly.
Furthermore the question was one of the highest voted of the [best-practices] tag, one of the more troublesome meta tags we had, a honey pot for extremely low quality questions. There might have been some useful information in there, but popularity alone not a good question makes.
Closed is meant as a temporary state for question. A question that is closed is on the chopping block, so to speak. Either someone should make heroic edits to the question to fix the reason why it was closed, or the question will eventually get deleted. As to why this particular question was deleted at this particular time, I'm not sure.