I've been playing with Ancestry.com's online trees.
I entered in a bit of information on my wife's Freund family, including Conrad Krebs (b0rn 7 Oct 1818 in Goldbach, Bavaria) who married Margaretta Freund. This family lived in Davenport, Scott County, Iowa, after immigrating in 1854.
I entered in Conrad's date and place of birth from his obituary. I realize an obituary is a secondary source for a date/place of birth, but right now it is all I have.
Ancestry did an "automatic" match for Conrad and found many things that were misses, but it did find him in the 1870 and 1880 census. I attached these entries and images to Conrad, making certain not to attach the census to his 7 Oct 1818 birth in Goldbach. Yet the program insisted on connecting the 1870 census to that date of birth.
Problem? Yes. The census gives an age that leads to a date of birth of about 1818, most certainly not 7 Oct 1818 in Goldbach. This is implying the census says something it does not. If people are not careful, they will tie records to information that they do not say. I realize it may seem like a minor detail, but it is not. Saying something says something it does not is inaccurate and leads to all kinds of confusion.