Apple iPhone 4G - Manual (Page 218)

If you link contacts with different first or last names, the names on the individual
contacts won’t change, but only one name appears on the unified card. To choose
which name appears when viewing the unified card, tap the linked card with the
name you prefer, then tap Use This Name For Unified Card.
Linked contacts aren’t merged. Unless you edit a unified contact, the contact in
the source account remains separate and unchanged. If you change information
in a unified contact, the changes are copied to each source account in which that
information already exists. If you add information to a unified contact, that information
is added to the contact in each source account.
Linked contact information also appears at the bottom of an individual contact’s Info
screen when it’s viewed in a specific source account (that is, not in the All Contacts
list), which lets you see the Unified Info screen and the linked contact from each of the
other source accounts.
218 Chapter 26 Contacts