I was looking for a similar question, and already shared the answer I found on another thread where you asked the same question.

Private IPs are next on the list, according to Rayiu on this thread (https://www.digitalocean.com/community/questions/additional-ip-addresses-internal-network-ip-addresses).

But I believe it will not be possible to use the private IPs on inter-datacenters communication, only inside the same data center. So, to communicate form NYC to AMS you will have to use public IPs, wich will count in your data transfer cap.

We will be deploying private IPs in the future which will allow droplets in the same DC to talk to each other without any charges.

Currently using the public IPv4 address you will still be traversing the local network in terms of performance and latency.

We have not yet made a determination if we will be providing inter DC connectivity free of charge the simplest way to do so would be to merge the private networks across the locations however creating such a large pool can cause other networking issues so it's very possible that for communication between DCs you would be charged for data transfer.

Private IPs are a key issue for us. Very few of our usual deployment strategies will work without them. When you have private IPs working, please announce it loudly! :-)

I for one would sign up right now if:

1.) Transfer between VPSs (droplets) within the same datacenter was free of charge (like linode or rackspace).
2.) You offered private IPs.

Those two are currently deal breakers-- sadly (mostly for me).

Any luck with this

@kevin: You can follow the progress on private networking here: http://digitalocean.uservoice.com/forums/136585-digital-ocean/suggestions/3020028-private-back-end-network-support