Apparently still alive and well in some circles (agree with below that most uses are financial/credit/legacy apps). I worked at one of the largest developers of ISP modem infrastructure in the late 90's called Ascend. Company was purchased by Lucent. Just a few years ago I ran into a friend still with the company and mentioned that, globally, carriers were still installing new dial-up infrastructure to the tune of a few $100-million annually. Amazing.