I was looking through my direct ancestors to see if I had photos of headstones for those that could be available. I found that I was missing a photo of the headstone of my great-great-grandmother, Maria Elizabeth (born Geers), (married Menke), (later married Schutte). Her burial is supposed to be in a cemetery local to where my mother grew up. I emailed a cousin and she didn't have it despite looking for it a few years back. I went to www.findagrave.com and saw that her headstone hasn't been posted. I submitted a request for a photo of her headstone, then it occurred to me to "glance" through the site and see if I could find headstones of others in my tree "real quick" so I had all the information I could on my relations. It's such a tiny little town, there couldn't be that many people buried there, right?
Wow. Just wow. I've now been at it for a week, all the time previously spend researching has been used downloading headstone photos and sometimes filling out spots in the tree I was missing information on someone or even missing people. It's amazing how families in small towns inter-marry. No, there's no "kissin' cousins" but when you have a dozen or so surnames, each marrying into the others, it gets quite confusing. A simple little "let's get a quick photo or two" has turned into a major, "let's see if we can connect everyone in this cemetery". Since I'm probably halfway through the alphabet in this "small" cemetery, I think it's likely 75-90% of the people buried there are linked and will end up in my family tree. Although probably 60% were in there already.
I know it's not a primary or even a secondary source (I think I'd call it a backup confirmation and a few more details source), when the new information fits the information I already have, I'll take it as relatively reliable.