Verification is so important.
I find it most frustrating when people starting out on researching their family history accept their first findings as truth, without first checking all sources available.
Research is never that easy.
When I first started researching my own paternal family I was overjoyed to find a cousin in Canada whom I'd previously had no knowledge of...We corresponded for about two years exchanging any information we discovered, until I told her that a certain piece of information she'd found didn't apply to an ancestor of ours, but to someone of the same name but belonging to a different family. Sadly she took umbrage at me pointing this out to her and decided to continue with her initial finding. ...This meant she began to follow a person's lineage which took her into an entirely different family.....I sent her many pieces of information showing where she'd made the error of going into the wrong family, but instead of accepting this proof, she decided to cease corresponding with me....all very sad, especially if her descendants take at face value the false information she's put on her tree.
I know family history can turn out to expensive with all the certificates etc. we need to purchase to help us prove who our ancestors really were, but that's something we have to accept if we want to make sure of getting at the truth about our family's history.