I do not agree for cameras and other photo material. I am selling some right now on ebay because I am changing all my equipment. What I am selling is in perfect condition, has received great care all the time (for me, cameras and photo equipments are very precious ). In addition, I had the time to test it, and had no problem with it, so the chance to have a problem now is limited. And I know several other people who are also very fussy with their equipment.
But I agree, there is a big risk and you do not know what you will find. You have to decide whether you take the risk to have a problem with what you buy, and in turn, have a chance to save money.

For the rest I agree, especially with baby equipment.