A Vonage representative told me today that one reason why some people were shut out of their Net phone service was due to a bad broadband connection on their end. The explanation was a response to why Vonage customers outside the four cities cited in the "delays" weren't getting service.
Whether you buy the argument or not (I'm naturally skeptical), she brought up a good point. The Internet is not as reliable as good old copper wires.
When was the last time your land line was out of service for hours at a time? Even cell phones, notorious for dropping calls, don't see down times at that level.
I'm optimistic that the Internet will become more reliable as time goes by. But with broadband becoming a virus and spam playground, having too big a pipe may have its own consequences.