I think it really depends on the reputation of the seller and
whether there is any trial period.  For example, if someone here
tells me that there is a small defect in the lens, but it has no
noticeable effect on the image, I'm likely to believe them. And
if I get the right to examine and return it if dissatisfied,
then I would most likely take the chance. This is a small tight
knit community, and nobody want the reputation of being a
cheat..  OTOH, if someone on evilBay says it's mint out of the
box, but "I don't know nuthin about cameras man" then I just
assume it got tested, doesn't work, and they're playing stupid.
Or, in the lens example "It such a small defect I couldn't get a
picture of it" then it may very well have a knife gouge across
the front.  So, yes, I might very well by a less than perfect
lens, so long as it's disclosed and I'm not paying a premium
price. In my case, the limiting factor is usually the
photographer, not the lens.