What Comcast had to say when I asked them to add CNN HD to my channel lineup
Please keep in mind that a majority of Comcast east coast subscriber base has CNN HD

Dear Kevin,
Comcast is committed to deploying HDTV service. We are working to
provide as many high definition channel broadcasters as possible. Here
are some of the factors involved with expanding our high definition
lineup:
-the negotiation and contract process required to obtain the rights to
carry a specific high definition broadcast, such as TNT-HD and HD-Net.
-the increased bandwidth resources which are required
-the relatively low number of subscribers (currently only a small
minority of customers have high definition compatible television sets)
We will continue to explore additional HD programming opportunities as
more content providers make plans to offer their programming in HD
format.
We appreciate the fact that you took the time to let us know what is
important to you. We hope to expand our high definition channel lineup
as fast as we can. Unfortunately we are unable to provide specific
details regarding the launch of new channels at this time, please keep
an eye on your monthly billing statement as the announcement of any
channel additions will appear on those statements.
Please feel free to contact us if you have any more questions. You may
respond directly to this email. Thank you for your interest in Comcast.
Thank you for choosing Comcast.
Sincerely,
Charlie
Comcast Customer Care Specialist
