Michael John Neill on his RootDig Tip of the Day blog posed the question as to whether online family trees should be part of a reasonably exhaustive search, in his post A Few Random Thoughts on Trees Being a “Required” Part of a Search.
My answer would be, it depends.
As an example, my husband was descended from John Dirk Mulder and Mary Ann Jones. I had found John and Mary’s marriage record, as well as the christening records for 3 of their children in London, and index entries for the christening of another son in the Netherlands. Living in Australia, I have limited access to English and Dutch records, as well as the disadvantage of not being able to read records in Dutch. I knew that 3 of the sons (and the other son died youg) migrated to Australia. However, I didn’t know what had happened to their parents.
In this particular case, I would include searching online family trees in my reasonably exhaustive search. Since I’m only related by marriage, I hadn’t been told any information about this family. However, a direct descendant may well have more information. As it turns out, someone in the family did know what had happened to their parents – their father had been a Dutch sea captain who had died at sea, and their mother had remarried, in the Netherlands. She and her new husband had then returned to London, and later also migrated to Australia.
Now that I knew where to look, and what surname to look for, I was then able to find the records to confirm most of the information (I still haven’t confirmed the details about John Dirk Mulder’s death).
On the other hand, in the example in Michael’s post, he knew where his ancestor was from, but there were hundreds of online trees with conflicting information about his ancestor’s wife and mother’s names. In this case, it would be a waste of time going through all the online trees, in order to try and find the correct information. On Ancestry, their collections are divided into 4 main categories: Historical Records, Stories and Publications, Family Trees and Photos & Maps. Where there are so many family trees, my reasonably exhaustive search would be limited to the Historical Records and Stories and Publications categories, as they would be more likely to have any information of value.