As early as 2006, the US military was specifically considering ways to use or manipulate blogs. An official report on the question can be accessed via an article at Wired.
Among other things, the report suggests that “Hiring a block of bloggers to verbally attack a specific person or promote a specific message may be worth considering”. Also, that “Hacking the site and subtly changing the messages and data – merely a few words or phrases – may be sufficient to begin destroying the blogger’s credibility.”
Clearly, it is credible that military entities may attempt to manipulate or alter communications of both everyday individuals and press.