True, I've had several lines collapse that way. I put what I had on rootsweb a while back, but I made sure that I put warnings that it is inaccurate on it so that noone will take it as "gospel" (hopefully). That being said, on a few of my lines that, well, shall we say, "converge" at various points (cousin marriages), I've got a built in yardstick. I'm also lucky that my mother's side of the family, Cox, happens to be one of the most researched and documented names out there, at least from the colonial period on.

Edit:
Another interesting note is that my mother's side of the family and my father's side of the family, most lines, tend to be within about 150 miles or less in distance from each other at quite a few points in time. I'm just waiting for that find that ends up tying my two sides toegether at some point