said by TKJunkMail :

Comcast keeps losing basic video subscribers.
...
But the continual loss of basic video subscribers is a trend that will eventually cost them down the road as they have fewer and fewer cable connected customers.

said by MrMoody :

Yes. And why are they losing subscribers? Competition from FiOS and UVerse? Puhleeze, they're still a drop in the bucket and DirecTV/Dish have been around as video competitors for ages.

I think there are three primary reasons:

1. Semiannual increases far exceeding inflation cause people to get fed up and unplug.
2. ATSC is a such a huge improvement over analog in many places, people who try it on their new widescreen TV wonder if they really need a $60 escalating cable bill for an inferior picture. So unless they need HBO or ESPN, they unplug too.
3. Comcast's legendary poor customer service drives customers away as well.