Dan Moren, Six Colors:
I put “merge” in quotes, because unlike the OS X feature, the contacts in question don’t seem to permanently meld together; the feature simply unites the cards as one for the purposes of viewing. Unlike OS X’s solution, iOS’s solution is non-destructive; you can separate the records at any time. Hence why it’s called “link” contacts instead of “merge.”
Interesting approach. Like Dan, I didn't know about this feature.