I subscribe to my local Time Warner's "basic" package for $13/month or so. This includes channels 2-14 in standard definition, and a handful of HD versions of those stations. I have no special equipment - the coax plugs right into all of my TVs. These HD stations have come in fine for quite a while for myself and others that have TVs with a QAM tuner. A few days ago, people stopped receiving all of these HD stations.
I have not contacted Time Warner yet, but I spoke with people who have. Some were told to use an antenna to receive HD, and another person was shipped a DTA. (Isn't a DTA worthless if you have a QAM tuner?)
My understanding was that a QAM tuner was all I needed and I would continue to receive the HD channels. I didn't think this was something Time Warner could arbitrarily take away.