I had the opportunity to have lunch with Tom Bolioli of Terra Novum. Tom is an interesting guy who is very much involved in developing the new Energy Star standard which covers (amongst other things) enterprise servers. One of the more controversial parts of the new standard is that there is going to be a measurement protocol to provide a standardized baseline; previously, Energy Star just plugged a meter into each device and set the standard at the top 20 percent. This new measurement protocol is an extra step to account for the complexity of server configuration these days, and is also an effort to fix the existing system where each vendor develops their own method.
While every scheme has its drawbacks, I'm with James Murray in that I see it as a "pretty effective compromise". Of course, if some players don't like the rules of the game, they can always try and do it on their own. Tom was optimistic about the adoption of the new standard, not in the least part because Energy Star is well recognized and is a brand in itself. Vendors can try and do their own thing, but ultimately if most go with a single standard, it will be hard for a 'rogue' standard to gain footing, particularly when such a rogue will benefit a specific vendor.