Too many of these posts and people will be paraphrasing line 230 from Act III Scene II of Hamlet.
However, while this isn't the reason I am researching my family history, I believe I have found support for at least one more, and I'm close to another of the 'famous people' Ancestry's One World Tree claims my grandmother, Myrtle Van Every, was related to. I've had fun laughing at some of the impossible family trees the OneWorldTree software draws, but the lousiest ball player will occasionally hit the ball.
(And researching both hits and misses can result in extending lines further back)
Alas, the hits are not necessarily the hits I'd have chosen.
According to this Genforum post, the book "Ancestors of American Presidents" claims the Eddye family is related to three Presidents: Ford, Benjamin Harrison, and Fillmore. I already knew about Harrison since the Van Every's intersect slightly more recently than the Eddyes. There are a couple unproven generations on my grandmothers side still for Fillmore. But if the book is accurate, Ford was 'definitely' my mother's 8th cousin. (I bet she wishes she knew this when he was alive.)
The book was researched by Gary Boyd Roberts, who seems to have some credentials. Senior Research Scholar for the New England Historic Genealogical Society sounds impressive. Since he seems to be known as a scholar, I expect the book to cite sources. It's out of print, though. I can buy it at Amazon for $300. Or I can browse through it at either the St. Louis County or St. Louis City library next time I go there. I think I'll do that. It's supposed to contain the ancestries of all the Presidents (Since it was published in 1995, it might include Clinton, I'm not sure.)
Find a library near you that has it