My big bad national ISP used the same PPPoE authentication for dialup and DSL. So you could buy an unlimited dialup account and use those hours on DSL and chew through as much data as you wanted. Later on, some independent ISPs sold logins+passwords that you could use over the "Bell" DSL service and connect through them for unlim data.

(I initially hated it when they switched their DSL service to PPPoE over whatever they had before, because the PPPoE overhead sucked up like 10-15% of your throughput... until I decided to run a little test...)