When IEEE 802.3ba was originally proposed their were multiple possible speeds that were being discussed, including 40, 80, 100, and 120Gbps. While there options were eventually narrowed down to just two, 40 and 100Gbps, the HSSG had difficulties decided on the one specific speed they wanted to become the new standard. HSSG chair John D'Ambrosia told PC World that although he "wouldn't say there was a fight, I would say their was an education going on, and it got heated at times." During the discussions two different groups formed, one which wanted faster server-to-switch connections at 40Gbps and one which wanted a more robust network backbone at 100Gbps. The higher speed required more expensive and power-hungry equipment, you can find out more about it from this presentation [PDF].
Unable to come up with a consensus the HSSG decided to standardize both 40Gbps and 100Gbps speeds as the IEEE 803.23ba standard. Each speed will use different connection equipment. 40Gbps can be 1 meter long on the backplane, 10 meters for copper cable and 100 meters for fiber-optics. The 100Gbps standard includes specifications for 10 kilometer and 40 kilometer connections over single-mode fiber.
According to D'Ambrosia this is the first time the specification group has approved two different speeds in the same specification. If IEEE approves the specification it could be completed by 2010 with devices that support is soon thereafter."