I've seen quite a few old questions that share some common denominators.
Question approximately 1+ year(s) old.
Little to no comment interaction with questioner
User has not logged in since the question and has only a single point.
User is not a member of other stack exchange sites
Here is an example of the questions type that I am refering to.
Under these particular circumstances does it make sense to close the question out?
I am of the mind that it does make sense as some of these lingering questions that are enumerated by search engines send recipients of these links to this site and they get nothing out of it as the question is still opened. I see the open questions under these specific circumstances and contamination of the site.