Originally Posted By: pennyless
Another misuse of apostrophes which is one of my pet peeves is the use of a name on a mailbox or a doormat, which reads "The Smith's" (insert name) rather than "The Smiths".... unless the family is bragging about their ownership of the domicile (and even then, assuming that there is more than one Smith living in the residence, it should read "The Smiths'")

The Smith is the head of the household. The usage is the same as the head of a clan being known as, e.g., The MacGregor. The possessive is used to indicate that the house is owned solely by The Smith, the one with the name on the deed, and not shared with the bank. I.e., the mortgage is paid off.