I had some involvement at MCCDC in reincarnation of DO back in 2004(interestingly, many of the "usual suspects" from the USMC Hunter Warrior experiments).
What I don't like about the current USMC definition is that it describes units operating out of mutual support range of one another. I think that the whole point of DO is to redefine, through training, education, technology, etc. what exactly "mutual support" is and what distances it can be effected at.
It seems that much of modern warfare is simply the story of the tug between dispersion and concentration (look at Napoleon's corps). There are many variables: communications (to coordinate external fires and logistics), mobility, internal fires capabilities (that has to balance for mobility and logistics), training and maturity (how independent can units operate depending on the environment).
DO applies to every unit in every mission--its just how physically dispersed they can be and still be able to mass the appropriate "effects" (whether these be fires, civil affairs, training indiginous forces).
The current thrust of USMC DO seems to be to validate small unit infantry organization and equipping. I welcome DO if it means we're putting brainpower and $$ to supporting squads (compared to the money we put towards aviation and other big items).