Secondary sources are sometimes all we have to go on. Sometimes things might even be a "third" source, such as transcriptions of tombstones. I would guess that most people who have done research in Frederick county knows about Jacob Holdcraft's book Names in Stone. For those that don't know, Holdcraft went around Frederick county in the 1950s and 60s transcribing all the tombstones he could find, he found some 75,000 stones in about 300 cemeteries. However, before he wrote his book, he published a series of booklets done by cemetery.
These books are an invaluable resource for researchers. However, because of the number of times the names were written and re-written, there can be problems. These problems can compound, when 50-60 years later someone tries to find an older cemetery. One such error is the Miller family cemetery, Holdcraft number 22, in Highland, which is between Myersville and Wolfsville. In Names in Stone, he gives the location of the cemetery as being near Harmony-Ellerton road and Wistman Lane, however, in pamphlet number 5 the location is given as the intersection of Harmony-Ellerton Road and Fishers Hollow Road. These roads are only about a half mile apart, but when looking for 6 stones in the over growth it's almost impossible to find.
Twice now I have been out looking for this cemetery, but now don't know exactly where to look. On a Sunday morning there are not a lot of people out to ask, and I have been unable to find the cemetery and will have to research further.
Another error, that also made it's way to Find a Grave is the Summers family cemetery. Holdcraft gives the location as being on Church Hill Road and Ward Cline Road. The person who originally submitted the cemetery to Find a Grave did the same but also added the latitude and longitude of the intersection. When I went to take photos of the cemetery I originally thought the cemetery was gone as I was in the wrong area. Luckily I saw someone mowing their lawn nearby and it turned out that she owned the property that the cemetery was located on.
So what does this say? It says that, if at all possible to find and use original sources as much as possible. It's not to say that secondary sources are bad, quite the opposite, sometimes it's the only thing we have left, we just can not rely upon them entirely.