A lot of free services would disappear if they were unable to make some sort of ad-based income. Some people would be unable to do anything except whatever was provided by their government without ad-supported services (thinking Google products, YouTube, etc.) It would eventually go back to the way it was in the old days - a few actually-useful-but-struggling sites, a few paid-for services that might or might not survive, a passel of vanity sites and some incoherent cranks and weirdos (Time Cube, etc.).

Heaven for some, but mostly boring for everyone else after an hour.