Forgive me if this has already been covered... but I'm just wondering what makes NC so special for server farms?
You missed all the posts so far about nukes and cheap power? (also cheap coal power there too, but willing to bet Apple might not stress that part.) That's a bigger tipping point than network backbone. Willing to bet the electric bill every month is still higher than the network bill (even at the low rates they are getting by locating there).
More importantly though, there is EXCESS power available. Google, Microsoft, etc are hunting in areas that had high power consumers and now are shutdown (e.g., large number of closed factories usually does this if they weren't co-generating their own power). Makes no sense to go somewhere were plugging in a new "small town" of power would make the grid flaky.
There are lots of places where can plug into the major arteries of the internet. However, not all of them are going to give you the right combo of no taxes (for extended period of time) , cheap power , excess power , suitable real estate to sit on with some privacy, environmentally suittable (no multiple threats) and cheap, cool water if installing major water chillers.
[ that's said I don't get what microsoft was thinking with something in Texas. Natural chilling is cheaper and more effective. Makes no sense to go somewhere it is very warm most of the year. You don't want data centers where the temp tops 100 with regularity during some months. ]
Also far away from California (the other data center(s) ), but not too far.
That gives them disaster recovery options (e.g., major earthquake in CA fail over to NC or major storm in NC fail over to CA ) and well as load balancing options ( East Coast and Euro/ME/Afr traffic to NC and west coast and AsiaPac traffic to CA ).