1> How does one deactivate accounts and what is the consequence?

You could Unregister a device and unplug it but at anytime you reconnect it you can re-register.

2> How do I move my Dockstar account to the new Pogoplug w/o a complete deactivate/re-activate process?

You use the same account for both devices. If you have them both plugged in and connected to your network when you go to my.pogoplug.com you can see both pogoplugs listed. So when you get your new one just sign in and activate it. No deactivation is needed.

3> Is it possible to keep both Dockstar and Pogoplug active?

Yes

3.5>One could be more secure (SSH) at the price of slower connections. How do I set that up under one master account?

Shouldn't need to do this with both active at the same time.

Place Shifting Enthusiasts