That is where you have to be extremely careful. There are a number of errors people have propagated on the trees present in Ancestry.com ... not trivial stuff either. Incorrect families associated with the wrong parents (which leads to a bad tree) are just starters. If you are not very careful with what the match suggests, you risk your tree becoming what would be considered as a junk tree to other researchers and a false genealogy that is doubted you want your family to believe as their genuine background.
After you are doing this for a while, you will come across this... often to the point that the "hint" or matched web record is just better off being ignored & rely on manual methods instead.
Good and accurate trees take real detective work. Use those trees out there as being at best "clues."