Several relatives of mine have done extensive work on their branches of our family tree. I came to recognize the importance of giving sources for information when I was working on extending the trees 10 years or so ago. The elderly relative who did much of the work over the past 40 years had sources, but she has not included them in the computer files.
I recently purchased an upgrade to Family Tree Maker. I feel like I need to dig out and cite the sources for the information in the tree. The new version of FTM has a green leaf next to an entry that has potential links online. Her link yields seven (!) family trees with a woman of the same name, all of which list her birthdate as 1745, while our tree lists it as 1741. As her spouse is also listed, it’s clearly the same individual, and the consensus date is 1745. However, when I look at the source given for the 1745 date in the various trees, the source is “Family Tree Information: Detail: Ancestry Family Trees.” This is the sort of situation where people are citing each other, and nobody is giving an actual source.
Edward, you've encountered a very common problem in genealogy. The first is the issue of folks merrily copying information they find online without verifying that it is correct. To verify, they need sources. And they need sources which clearly indicate where the information was found (a book, a microfilm, an original document, Aunt Harriet, Gramma's recollections, etc). Once a researcher knows what the source for the information was, they can determine if the source is reliable or not.One question that occurs to me is what are considered legitimate sources for information on direct family members (my grandparents, parents, siblings, children and nieces/nephews). Do I need actual birth certificates and death certificates (or obituaries) to document their particulars, or is word-of-mouth within the family good up to a point? (I know all the particulars to-date).
For example if I find a record of my great grandfather's birth but the source given is "Gramma Smith told me this" I am going to question that source. It's family lore and may or may not be correct.
If however the source provided is a church register or some other reputable source, I'm going to accept the data with one caveat - that I need to find and verify that source personally. Why? Because the researcher noting it may have erred when copying it. I want to see it for myself before adding it to my family tree. And it's always best to go back the original rather than trust a transcribed or extracted version.
Family Lore & Memories
The second question you asked was whether or not family memories were good enough. I'm afraid they are not. They should be used as clues for further research. You may find a source that verifies the family memory. But you are as likely to find a source that indicates that family memory was faulty, or only partially correct.
An example from my own genealogy research is that of my uncle who wrote letters in the 1960s stating, among other things, that his maternal grandmother was born in Elmvale Ontario. Since I knew nothing of that side of the family and there were no older family members to question, this was a great clue. Notice I said "clue"!
My research found that great-grandma Peer was not born in Elmvale which is in Simcoe County, but was born in another county entirely, many miles distant. However my uncle's statement was still important because it turned out that the family moved to a town near Elmvale when great-grandma was a teenager. So my uncle's statement was a great clue, but was not correct as he gave it.
The Shaky Leaf
Last point - the Ancestry.com shaky leaf. You will find genealogists who love the shaky leaf and those who despise it. I personally like it for clues but not as a definite "this must be correct!" result.
Sometimes the shaky leaf leads you to online family trees which the conscientious researcher will use with caution. Sometimes it leads you to gold - an online record that includes images of original ledgers or certificates. Naturally you can trust an image of an original record. As with any source, analyze and evaluate it before accepting it as correct!
To read more about verifying sources and being cautious with online family trees, take a look at