Just because a question doesn't have an answer now doesn't necessarily mean it won't receive an answer at some point in the future. Therefore I don't think it makes sense to delete questions just because they don't have an answer (yet).
However, I do believe that curation of questions is valuable. There are quite a few bad questions around here that most definitely deserve deletion (some of which even have answers, for instance the classic "I solved my problem" with no indication of what the problem actually was or how it was solved, which makes both question and answer useless for anyone else).
Personally I like the Stack Overflow model where curation involves a number of factors:
- community moderation (by members who gained enough rep)
- moderation by elected moderators
- moderation by staff
For this to work I believe several things would have to be changed, though. For starters, the ability to vote on questions from the question list would have to go. From what I observed questions gain significantly more votes than answers, which I attribute to people voting (maybe even serial-voting) from the questions list. This effective vote imbalance gives the people asking questions far more importance than the people providing answers (and would also give them quicker access to moderation tools).
Flagging would have to be improved, too. Currently it's just two flags required for hiding a post and there is no indication for the reasons behind the flags unless the people flagging also post a comment. It would help curation if people could provide/select a reason for the flag (e.g. question not answerable, spam, rudeness, ...). I'd also prefer if at least 3 flags were required for hiding a post (better yet, close it instead of hiding it).
People should stop locking (closing) questions that they consider answered. The proper indication for "this question is answered" is to accept the respective answer. Closing/locking questions should be reserved for stopping people from answering bad questions.
That's my 2 cents on the matter for now.