If a question doesn't live up to our standards, we should close it, preferably as off-topic with our shiny new custom close reason.
This allows the question to retain its visibility, and for potential answerers to form potential answers. Edits can take place to specify the question further, and it can be reopened without necessitating mod input - the community can both close and reopen.
Again, @Undo tells me that on SR, low quality answers are deleted straight off the bat. The user is linked to the quality policy, given a brief summary of what's required, and told to edit or post a new answer.
I think that's a policy worth following. Since we can't "close" answers (and I don't even know how that would work), deletion removes invalid and bad-precedent-setting answers from view, and gives the author the required details to post a new one.