Just because somebody wrote that your ancestor is related to Joe Shmoe doesn't mean that it is true. How can you tell if it is true or might be true? Look for footnotes citing documents that support the statements or at least a discussion of documents leading to this conclusion. You will have to judge if the documentation is enough to support the theory. Even better would be to search out those documents yourself and make your own conclusions.
Several months ago I had a cousin of sorts contact me about a common Fry ancestor. I mentioned that I was aware of several ancestors through family lore before our common one, but that I hadn't made a paper/document connection between them yet. During our conversation this cousin told me about the Heinrich Frey Family Association. My cousin said the connections were all right there. I was very excited.
After getting off the phone I immediately Googled the association. I went to the page with the generations outlined, scrolled down, and there was our common ancestor, Jefferson Fry! This was great! I scrolled down further and discovered.....not a single citation to support any of these statements. Argh!! Even worse (better?) I found a mistake. There is a girl listed as Jefferson's daughter and it is not true. I can prove it. For a few years I've had a hypothesis about who she was, but had not been able to get my hands on anything to support my theory. This past summer at NARA I found a Homestead Land Record that gives a wonderfully detailed description of her relation to the family. I would give you more details, but I recently I had the sudden notion this could make a great case study write up. So I'm saving it for the time being.
Now, having said that there were no citations on this website, I do not mean to imply that all of these statements/connections are false by any means. By wandering through the site I was able to tell that some people have actually put in a lot of research time to prove connections. For whatever reason the website has just not included citations. I guess I'll have to contact them and find out why.
When researching family history a bit of skepticism is healthy. Personally, I think it makes you a better genealogist. It doesn't mean that you have to call people out on their research and make a fuss. However, it does make you think for yourself and construct your own conclusions.
Note: If you are related to Jefferson Fry and want to know about the girl in question, email me and I'll tell you what I found.