Marilyn, I'm afraid you're preaching to the choir on that one. I've had experiences like yours, and worse. I've up against a brick wall with my great great grandfather. His name was David Tucker. I got a tree hint and the owner of the tree had TWO David Tuckers listed. I think a woman in the middle of the 19th century would be more likely to have a kid at 55 than have a family that named TWO of their kids the same name.
I think the big part of the problem is with Ancestry.com itself and their commercials. I have a feeling that some people think that if they get a shaky leaf, it MUST be their ancestor, no ifs ands or buts. Not sure how to do anything about that short of forcing people to read through a couple of pages of basic instructions and tips before the site allows them to start a new tree. Even then, they could put it on the screen, but there is no way to guarantee that people would actually read it.