I doubt the chart is a huge surprise for anyone following the industry, but it still does make for an interesting graphic. Despite all the advertising money that Vonage can throw out there, Comcast and the other cable providers have the inherent advantage that they can easily offer powerful "triple-play bundles" of cable TV, Internet access and phone service.
Comcast is no longer my provider (Time-Warner services Keene, NH, where I live.), but when I lived in Burlington, VT, we had Comcast for Internet access and Verizon for phone (and we didn't have anyone for TV, since we don't watch it). The offers that Comcast kept sending us, though, encouraging us to switch, were quite compelling. The amount I paid for Internet access would have been lower if I had either phone or TV with Comcast, and even lower if I had all three.
If we actually watched TV and therefore wanted cable TV, the economics of the "triple-play" would be very hard to beat... so it's no surprise at all to me to see this chart. I would expect we'll continue to see the growth of one and the continued stagnation of the other.
What would be more interesting to me would be to see the subscriber growth of Comcast versus the other MVNOs and the DSL providers. Fascinating times we live in...