Think about it this way: what's the minimum improvement you'll pay a whole heap of money for? Each generation gets introduced with new switches, new NICs, and

Think about it this way: what's the minimum improvement you'll pay a whole heap of money for? Each generation gets introduced with new switches, new NICs, and new cabling. Since 100Mb it has been possible to have link aggregation groups, where two or more cables on the same number of NICs on each side are bundled together into one bandwidth device. At some point you need to decide that it's worth doing the transition -- and 10x is a pretty good number for that. The recent oddballs are 50G, 40G, 25G and 2.5G. All of them come from the idea of taking a higher speed NIC and adding a little more hardware to get multiple PHY transceivers -- a 100G becomes 2x50 or 4x25, and a 10G becomes 4x2.5. Oddly, 40G comes from 4x10G in the other direction, and is more expensive to produce than 50G equipment. It's not very popular.