This is a question the entire fediverse needs to wrangle with. On the one hand, advertising has had an unquestionably negative impact on the Internet. On the other, these services DO cost money to run. While in a perfect world donations would cover everything, the reality is most users of the platforms/communities aren't paying to support them. If we don't all figure this out, it's going to be hard for the fediverse to scale. Would love to hear ideas in the comments!