Being convicted to dialup and GPRS almost six months each year I am getting the impression that more and more sites simply become unusable on these basic speeds. Especially sites with many Ajax callback routines easily timeout because the delays in every call to the home server add up.
People in remote locations also often rely on the Internet for large purchases. I fairly often book hotels and flights via dialup and GPRS because there are no travel offices nearby where I can go. Just two days ago I spent 50 minutes on the Internet just for the checkout process of one ticket and one hotel. Total spent money more than $1000. If there had been more than the smallest alternative to book the ticket and hotel off-line I would have used that option.