Address Book on OS X has a neato “Find Duplicates” feature. But it doesn’t do everything I need it to.
On a mobile phone (Nokia ones, at least) if you have more than one contact with the same number, it gets confused when one of them calls, and doesn’t know who to display on the caller list.
So, a proper “Find Duplicates” should find the same number, and even further, the equivalent number if using +countryCode numbering, and allow you to choose who gets to keep the number.
This is most noticed at workplaces, although when you have a couple, such as your parents, who have the same home phone number it also manifests. That is, assuming your parents are still living together, anyway.
I might have to knock together an AppleScript to do this. (This entry is a note to self about that).
