I think finding a good revenue model is fine, as long as the orgs that host these services are transparent in how they operate and have business models that are not focused on 10x growth year over year. Selling Ad space has always been a good model as long as you maintain a healthy separation from your Ad customers and your regular users. Data mining is always a huge money maker but then you violate your users privacy. I wouldn’t know how to build this into lemmy or other apps but an idea I have had lately is having a sliding scale for users to decide what info to share with advertisers as well as giving the user a percentage of the money that was made on their information. That way the org hosting and administrating the service gets funds to keep the site going and their users are compensated for the sale of their personal information.

The problem is if you run as volunteer only you can only recruit from people who are socioeconomically privileged enough to volunteer. Having a revenue model isn’t always about making a single person rich, it can be about being able to properly compensate people for their time, knowledge and experience who otherwise would not be able to because other responsibilities prevent them from it.