With the USAF's history of being responsible for a range of national-level intelligence and networked operations, they might have been seen as the logical armed force to establish the electronic defences for the USA. However, the argument could be made that the NSA or FBI might be better suited for defending the electronic frontier in terms of their historical mandates.
The US Army is looking to have the Network Warfare Battalion not only support the US Army but also the US Department of Defense, something which might be seen as stepping on the toes of the USAF Cyber Command. Instead of the Army / Navy football rivalry, perhaps there will be a Command & Conquer rivalry between the units to establish bragging rights as the pre-eminent network warfare unit.
Potentially the most important aspect of the Network Warfare Battalion is that it centralises the existing US Army computer network operations and so will deliver greater efficiency for the Army from its existing operations support, as well as the expanded future scope that it represents through 'Network Warfare'.
Some critics might point out that while network support and offensive and defensive network operations (the attacking and defending components) are related, they aren't closely related enough for this consolidation of resources to work quite as well as the US Army is promising. It will probably lead to greater resources being available to support network operations, but it is likely to see those capabilities become the third wheel of the battalion once the offensive and defensive capabilities are fully developed.
With more and more armed forces globally admitting to having, or newly creating, network warfare units, it is highlighting the growing importance of what some are considering the fifth realm of the battlespace (Sea, Air, Land, Space, and now the Network). Others merely see it as a logical extension of Electronic Intelligence (ELINT) and Communications Intelligence (COMINT), and therefore nothing special.
The final say as to whether it is a new realm will come when the newest special forces unit is created - the SNAILS (Sea, Network, AIr, Land, Space), to replace the SEALs (Sea, Air, Land). Humour aside, this is something that a lot of money and resources is being devoted to by military institutions around the world. Even if the fifth realm doesn't exist yet, it seems inevitable that it will be created and fought in. Soldiers may not die in its battles, but the wider community may be affected when networked financial systems or public utilities are attacked.