Some of the photos are uploaded directly to the server and are hosted for awhile - a year or so, before getting cleaned out - that's why they disappear in the older threads. Others are linked to another place on the Internet. If the link is OK, the photo continues to be visible. If that link is broken, the photo goes away. Some of those photos are only up for a short time. For example, I'll post an occasional thread showing some cool Mopars in my area that are on Craigslist (SoCal Mopars), usually with a photo link. But when the ad gets wiped from CL, the photo link goes with it.