Those people who repeat old posts are spammers, and their software pulls an old post, the older the better probably to avoid detection by the human eye, and usually "stuffs" a blank or broken image that contains a tracking / referral link, so if you load their image and then shop at Amazon, whoever they are is probably getting a kickback and you don't even know any better. Sneaky stuff. If they haven't stuffed an image into it, then they are just making "real" posts to make them seem non-spammy and then hit us with a link a few posts later.