I agree with you (and Putnam) that television has eroded our social networks, probably more than anything else.
Another point that you might want to address (or I could in a linked In-Depth Discussion Topic) is that television has turned our national political conversation into a one-way interaction. This is one of the central points in Al Gore's latest book "The Assault on Reason." People have become passive recipients of information about the problems in our world because the primary communication medium is television, and it only flows one way. So in addition to the points you raise -- that television is controlled by powerful corporations, and that people are far more brainwashed by watching it than they realize (points which Gore touches on as well) -- there is the fact that television watching erodes political activity, like all activity, because there is no way to actively engage with your television. It's hard to think critically about what you're hearing when there is no way to ask questions or respond, when you are consigned to a listener and observer role, and no one is asking your opinion.
Thanks so much for posting this. It's a very important issue, you have framed it very well, and I look forward to reading more!