Odds are good some questions will come up which no one currently on the site has a (good) answers for. What is the protocol for handling such questions?
You could post a link to the question on your blog, Facebook page or Twitter (for example).
If you use the URL from the "link" link then this includes your user id and visits using that URL are tracked. If you get enough visits within a given time period you might get the "Announcer", "Booster" or even "Publicist" badge.
From what I read in the FAQ, if a question is edited, that can bump it back up to the top of the list. So if some time has gone by and you have edit privileges, you could clean up the question a bit.
This actually has the added benefit of not just bumping it to the top, but also it helps make sure the question is clear, readable, and easy to understand. All of these things will help increase the likelihood that more people will be interested in spending time trying to answer it.
I am not sure I understand your question -- if you see a question that isn't answered, and you have the expertise or knowledge to answer it ... why wouldn't you?
The only time I would refrain from answering a question is when I know it is clearly off-topic, e.g.