So your ancestor's name is just too common - Smith, Jones or some other name that you just can't seem to narrow down the field with? Look at the neighbors find the most outrageous name, either given or surname and search for that.
Yes, I know if they moved or if your family moved you'll be out of luck. Chances are you'll be fine and hopefully successful in your search. Sounds better than going thru 975,689 entries searching for John Q. Smith.