One point that's interesting to me--the variability of names. (Maybe I've already mentioned this, if so I apologize.) Obviously, I assume that the Platonic "ideal" of my family name is "Harshaw". Anything else must be a deviation. But when you search, you find lots of "Harshas"--obviously a branch of the family that got a little lazy, dropping the superfluous "w". But there's also a "Harshe" recorded in the census--what's that about--some census taker who couldn't really spell? And "Harshy"--did people mispronounce the true name all those years ago?
And a "Hershey". Now we're really getting into trouble--is it possible that we're really the unrecognized heirs of the founder of the Hershey chocolates and Hershey, PA? And what does this do to the search? Do you try to follow all the variants down all the rabbit holes? Ancestry.com uses the "Soundex" system in searching (I think--Soundex being a formula that converts variant spellings into one set of sounds) and therefore turns up a lot of "Harrises". Do you seriously consider the possibility one or more of those results is the misrecorded offspring of a "true" Harshaw?
And all this is without getting into other sources--like Germany for "Harshas".