Y'know, Geminispace probably won't be free of ads forever. Assuming we don't abolish capitalism within the next few years, eventually someone is gonna pay someone else to shill their stuff on their gemlog. It's just gonna happen.
Gemini does, however, seem like it'll be uniquely resistant to capitalist invasion. Off the top of my head, here are a few possible ways it might go.
As previously mentioned -- someone with a popular gemlog gets offered some money to shill someone's product. If Gemini obtains any amount of popularity, this is largely inevitable. Sponsorships, thankfully, tend to be among the more tasteful and tolerable kinds of advertising.
A feed aggregator becomes incredibly popular and important for Geminispace. The feed operator offers to give "top billing" to capsule owners willing to pay money. This isn't a huge problem though; you can just go use a different feed aggregator. Compared to something like a search engine on the web, feed aggregators are easy to set up. Plus, the protocol is simple enough that throwing a lot of resources into a capsule won't actually make it better than an amateur one.
EvilCo comes along and starts offering a Gemini hosting platform for technically-challenged people. This platform becomes very popular. Under the hood, it's running a custom Gemini server, rather than any of the open-source offerings. They also produce a Gemini client, far more professional-looking and full-featured than any of the other offerings. Naturally, folks flock to this one too. Then, EvilCo introduces a new update to their custom server platform and their custom browser, adding off-spec features. People using their platform and their browser come to expect these features, and feel that on-spec Gemini capsules are "behind the times." Then these new features are used to serve ads, or track user data, etc.
However, I don't know that this scheme would actually be very effective. If your capsule is "behind the times" you can just...stay that way. If you want fancy features, the Web still exists. I think capitalists will try it, and maybe succeed at creating a more web-like section of Geminispace. But you can just not go there. I don't expect anything important will be hosted on those platforms; businesses are always going to prefer the Web, and it's not going anywhere. You just stick to an on-spec client, and you're safe. And since the protocol as it stands is so simple, community Gemini hosting will always be around. And it's kind of hard for a for-profit business to compete with "just ask Craig for an account, he'll set you up."
Let's be honest, all of this is predicated on the frankly MASSIVE assumption that Gemini will take off in a big way, rather than staying niche. And to be honest, I don't know that I see that happening. I think it'll grow, definitely. But will it ever get large enough to actually get on Big Tech's radar? I somehow doubt it. I'd honestly be surprised if it ever became popular enough to be, say, added to Firefox. And I think like Alex Flounder's "Useless Tree," Gemini will prove resilient against invasion. It's just not worth the investment.
oh yeah baby this was "Re: Gemini is Useless" the entire fucking time yeehaw