Ethernet is most ubiquitous. You don't need physical access to a server with data, just network access. Most environments outside of datacenters don't have 10GbE switches or NICs yet.
EDIT: It appears it supports 10GbE natively. I assume it'll also support lower Ethernet speeds.
EDIT: It appears it supports 10GbE natively. I assume it'll also support lower Ethernet speeds.