[Disclosure: My initial, unflattering, and perhaps embarassing "contribution" to this thread remains for posterity in the revision history. In order not to be a censor, I needed note that.]
Many of those popular/famous questions seem to have started life as regular questions, then they become community wiki (cw) either procedurally from comments and moderation, or programatically once a large number of answers are contributed over time. While cw questions cease to gain points once they're categorized, they continue to rack-up badges, so it seems they are not officially discouraged.
But you ask this question that starts, "Is it generally frowned upon to.."
..and it suggests a sentiment I've detected, myself, like when I see a comment like this floating below a question, sometimes an interesting question..
For some reason that upsets me. And the "3" to the left of it feels like a ganging-up.
The worse part of it is, there is something contagious about that behavior, and I've found myself getting the urge to jump on those cw questions, too. Could it be to get those comment up-votes? I sure hope not. Is that comment really "adding something useful to the post"?? (..bothering me even more is the fact that I even care. What gives! Where does this rule-crazy sentiment come from?)
So there is a situation here I can't resolve. Basically I can't feel good about either asking open questions, feeling the guilt and the stigma, or hustling at the chance to get comment votes for my keen ability to segregate the real questions from those.. other questions.
Nevertheless, on the final analysis there are some pretty great cw questions, and I'm glad they were asked. Otherwise, I would never have known about Clickie, among many other odd bits. They definitely contribute something useful, and they shouldn't be frowned upon, but I'm at a loss to explain the mysterious stigma surrounding the cw threads. Whatever you picked up on, I've definitely picked up on it, as well. :/