The Higher Speed Study Group (HSSG), a working group within IEEE, has divided into factions battling it out. The original charter of the group is to explore a 100 Gbps ethernet standard. However, many members are pushing for a 40 Gbps ethernet standard to be established as well as a stepping stone to the ultimate goal.
The 100G proponents are resisting the idea, claiming that it will take their focus off of their real purpose and will impact progress toward the 100 Gbps standard. Those in favor of 40G feel that it is a logical step that is on the path toward 100G and gives the market something to deliver in the mean time.
The battle has gotten a little nasty and IEEE has directed the factions to come to a consensus and get things on track, or IEEE may possibly dissolve the working group altogether. Read Controversy threatens 100G standards work for more details.