Wow... you must be talking about iSCSI? There also was a specification to do copper and fiber via Firewire. That said Gigabit Ethernet.....
10Mbit = 1.25 Mb/sec theoretical..
100Mbit = 12.5Mb/sec theoretical..
1,000Mbit = 125Mb/sec theoretical..
10Gbit = 1.25Gb/sec = 1,250Mb/sec theoretical..
As you can see, eSATA smokes nearly all of them even at eSATA 150 (150Mb/sec). The fastest version is 300Mb/sec for eSATA..
Right now the only way to locally saturate 10Gb would be with a sizable RAID at RAID 0, 5 or 6.
For example, if you were to take 10 2Tb hard disks (RAID 0) at 100Mb/sec you could yield (100Mb/disk * 10 drives) = 10 Gigabytes/sec.. which would more than saturate 10Gb Ethernet. These are very ROUGH numbers but they give an impression..