Many of the early ISPs played shell games with ad companies. NetZero is one of the most famously documented of the 90s dot-com age promising "free internet" with ads/MLM schemes, but they were one of the pack. The few I can recall today to google on the Bings, including NetZero, surprisingly still exist and survived the dot-com implosion as more traditional ISPs, but NetZero is the most useful example to give as it still bears the scars of its early scam-like history its own brand name. I don't think they've offered actual "zero dollar" service in more than a decade, but that's where their name originated.

I recall so many fly-by-night ads and ads+MLM schemes in the early internet, a lot of which I watched in Slashdot takedowns and teardowns at the time.