A colleague on SFCANADA mailing list, today (Aug 26, 2012), was fishing for people's takes on scientifically valid reasons why an intelligent civilization might not have good communications. Here's my response on behalf of the Okal Rel Unvierse. (Lynda)
My space opera (Okal Rel) includes broken communications in a few ways. First, because reality skimming connects worlds and it is faster-than-light, there's no faster communicaton than a pilot arriving. Bit like the old pony express. Reality Skimming requires a pilot. The pilots themselves are the bioengineered tech in this case but that's another story.
For inside environments I base communication impairment on oen materials science explanation and one social one. Hullsteel is based on "memory" aspect of advanced materials science thinking. It is like the "Wonderful One Horse Shay" (Reading no Youtube) of an old poem my father liked. It won't crack and can't be warped. It will take extreme stress. But at breaking point, it shatters to smithereens. It also bounces signals so you can't send radio transmissions through it. The social aspect I use is that communications takes a lot of cooperation on the part of the groups behind it. Agreeing on bands to use. Shared codexes. Leaving physical equipment alone if it relies on wires vs. transmission and not interferring with each other if it does require transmission. In UnderGelion, the hullsteel enclosed city where a lot of my "hub of the neo-feudal empire" stories are set, the families in power interfer with each other's communications. The situation, and various people's attempts to work around it, are peppered throughout my series.