Because genealogy is source based and source driven, one of the most frustrating aspects of doing genealogical research is to run into a situation where it appears that source records are missing, are wrong or have been deliberately changed or modified. Unfortunately, this seems to happen quite frequently. The missing record could be attributed to something as dramatic as a courthouse fire or as mundane as simply being misread and filed in the wrong place. Anyone who deals with numbers of paper records, realizes how easy it is to mislay a document or file it in the wrong file. When I was practicing law, I found hundreds of mis-filed documents, that is documents that were either out of order or stuck in the wrong file folder.
The fact that there can be missing, wrong or intentionally changed data addresses a basic limitation of genealogical research. Missing, wrong or intentionally changed data may become a barrier (brick wall) to finding additional information about an ancestor. In the past 200 years or so, it is very, very likely that there are additional records that will allow further research, but the further you go back in time, the more likely that such a record problem stops further research. In fact, if you go back far enough in time, you will always find that the records run out. As a rule of thumb, this occurs around the mid-16th Century.
But the idea that records can go missing or be inaccurate or intentionally altered has greater implications for the entire concept of genealogical research. Very few of us are "document experts" and we likely do not possess the skills necessary to do handwriting analysis and forensic document authentication. If you go back far enough, your ancestors likely did not read or write. How do you know that the "X" on any particular document was actually the "X" of your ancestor. Documents can be a very shaky foundation for building an extended pedigree.
This situation points out the tentative nature of genealogical research. Any opinions or theories you may have about your ancestral lines can be brought down like a house of cards with one false or missing document. As you go back in time the risk that your opinions are not well based continues to increase. I have been comparing both law and science to genealogy recently. In one respect they are similar. In science we have numerous examples of people who created false experimental results to support their theories. In law, we have perjury and fraud. In both law and science, there is usually a way that the fraudulent activities are eventually discovered and discredited. But in genealogy we enshrine those same fraudulent activities in millions of online pedigrees.
Law and science are community based activities. Going to court is a public activity involving many people in different capacities. The same thing happens in science. Scientists do not work alone. Their work is continually peer-reviewed for sufficiency and accuracy. Even famous scientific frauds of the past are eventually uncovered and corrected. For example, the famous Piltdown Man hoax.
Genealogy, on the other hand, is a solitary pursuit. If you build your ancestral family pedigree and then publish it, who will question your work. In fact, even if you later change your mind about the accuracy of your work, you will find your mistakes and inaccurate work copied all over the Internet.
Delving even deeper into the implications of missing et al. documents, it is evident that without a consistent and substantial way to uncover pedigree errors based on these types of sources, that the reliability of genealogy is in question. This issue goes to the heart of the reason why main line historians have resisted the idea of incorporating genealogy as an academic pursuit. I have, from time to time, referred to problems I found when I was doing my initial survey of what had already been done on my ancestral lines. Those same problems exist today. There is no mechanism inherent in genealogy to cleanse the pedigrees. In fact, the opposite is true, as time goes on, there is more and more inaccurate information out there accumulating.
As I have written before, the concept of a unified family tree gives a glimmer of hope that there will be a mechanism for "correcting" inaccurate genealogical data no matter where it has arisen. But for now it is a fraud and hoax ridden market where the buyer must beware.
The key to solving this dilemma is accurate and consistent source citations. Researchers not only need to generate them as they do their work, but subsequent researchers need to constantly evaluate and verify the accuracy of the source citations. If these activities were combined with a universal, unified family tree, such as FamilySearch.org Family Tree or a similar project, there is a possibility that we will some day be admired for our consistency and accuracy rather than the opposite.