What to ask when buying used speakers?

I have purchased used components in the past and I can do this with confidence their functionality is well defined and easily verified. I am starting to look for a new set of speakers and will consider buying used. Assuming that I am doing this over distance and will not be able to inspect or demo the speakers in person, what are some good questions to ask to determine the real state of the speakers? Any red flags? Can used speakers have incurred subtle damages or wear that will affect the sound? For the sake of discussion, let's assume that they are less than five years old so we can rule out decaying surrounds and old caps, etc.