AMD will soon launch a new 2.6GHz dual-core Opteron processors with a thermal design power (TDP) of 120W. This is 25W more than the 95W TDP of the 2.4GHz dual-core Opteron, but the processor will only be available to large OEMs.
The main reason for this is because this processor requires a new cooling and power infrastructure that isn't found on most motherboards and cases.
If you are building a box from the ground up, you can spec out more airflow and power, and it won't be a problem. Plug it in to a Tyan S2882 you have lying around, and suddenly it could be a problem. AMD doesn't want this, so it is only selling them to people that can deal with it.
Next year we can expect a 2.8GHz Opteron along with a 2.6GHz part with a 95W TDP.