You need an effective message to send, someone to encode that message, a medium for it to pass through, and a receiver to decode the message. Any part of that gets screwed up and the whole message gets screwed up.
Herein lies quite a conundrum for an organization the size of the Army. In order to help solve the problem of so many people needing to coordinate, integrate, disseminate, and communicate so much information, heirarchies are established with formal methods for communication up, down, and across the chain of command. Processes and controls (ie red-tape) need to be in place to ensure that the proper information is shared and not shared with the correct people.
This red-tape is often inherently frustrating to many people trying to accomplish tasks within the organization. An example is the extensive effort to get a football and frisbee for PT that I had to go through in order to even find out if the facilities had these items. First I had to determine the correct place to go to rent the items. After some phone calls I determined it was an MWR building. Upon contacting them, I was informed that in order to even find out if they had the equipment, I needed to get a signed memo from the commander (in proper army memorandum form) and have it faxed to the correct person. I told them we didn't have a fax (because really, who has a fax anymore?), and by the next day they were able to contact me back with an email address that I could send a scanned copy to.
Now in an organization of 10, you would just have to ask the person with the balls if you could have one, but in an organization so large you need to know the proper channels to go through before you can even begin. Further, a lot of the ad hoc policies become outdated and ineffective over time, but are never changed because nobody realizes there is a better way. What kinds of red-tape does your organization have that could be rid of? How could you change it?
Communication on team levels is also vitally important. We develop hand and arm signals, code words, radio communication procedures, and thousands of other methods of ensuring that the messages we send are decoded correctly and by only the intended recipients. Call-signs, the phonetic alphabet, and acronyms are just a few of the ways that communication is streamlined in small groups. These methods are in many ways much more effective than the communications methods used in many other organizations, because they have to be. If the wrong person gets the message, or the message takes too long to convey, then people could die or missions could be compromised.
Overall, communication in large organizations is an extremely difficult aspect to manage and to understand. However, with effective controls and policies in place, the communication can be conveyed properly.