This is a question I am facing. For example: My family can trace their roots back to a person named Ebenezer Denyer in Texas. We know he was a Confederate Soldier as we have a letter from his granddaughter, to the government asking for confirmation from their records, and their positive response.
According to a record at Family Search, Ebenezer's parents are William Denyer and Elizabeth Sliver. Which is as far as FamilySearch goes. However on Rootsweb there's a long descendency from Henry Rosenberger of Franconia. A Mennonite born in Germany around 1685. One line of the descendency ends at William and Elizabeth. Apparently all the information in this descendency comes from a book published in 1906 by an AJ Fretz. But I don't know AJ Fretz. I don't have the book. How much do I trust it?
I don't know the individual who entered the data at FamilySearch either so I don't know that Ebenezer's parents are William and Elizabeth. However, the county in Texas where Ebenezer got married does have the certificate, which might possibly contain some confirmation on that score; We'll see.
But it doesn't really answer my question. I downloaded the gedcom, and the Register, and told my mother she probably has a Mennonite minister as a direct ancestor. But I felt the need to insert the 'probably.'