Currently the 'spouse' system in the address book is simply a text field,
but it would be great if it was a bit more of a connection between two
contact entries.  IE: I enter 'bob jones' and all his contact and address
information into my addressbook.  If his wife 'jane' is important to me I
would enter her in as well, first as his spouse, but then a full new
address book entry for her.  Probably 50% of the information (home phone#,
address) could be potentially the same for these two people, but I have to
enter it twice.

I can see the evolution contact manager creating a system where when you
enter in a spouse ('jane') it searches the addressbook for 'jane jones' and
then 'jane' and pops these up with a 'are any of these the people you
mean?' message.  If not, then it would ask if I wanted to do an 'edit full'
for 'jane jones' and if so, duplicated bob's information with the exception
of obvious non-applicable data (name).  These days even IMs aren't person
specific, so even this and email addresses are POTENTIALLY duplicatible. 

If the user decided they didn't want a full entry, the system would leave
it as it is now, just a note saying that bob's spouse is jane.  If the user
did have a full address card for the second user, it could display an icon
by the spouse's name, where clicking it would bring up the address book
entry (or just indicating that there is a different entry for this).

I guess this might bring up a lot of questions about should the data stay
synced up, should you be able to not edit one contact card or not, but I
say just have this as a quick and user-friendly way to edit a spouses
address card without too much fuss or confusion.  

I realize this goes a bit beyond the paradigm of a set of address cards,
but after using the contact manager a bit as a user, and having several
friends with spouses and having to go through adding and cutting and
pasting duplicate information around, a system like this could be a real
plus to people using evolution.