From Casey Newton's 13 Predictions for 2023:

"Substack will launch an ad network. The Rebooting’s Brian Morrissey likes to say that the first step toward building an ad network is to first say you’ll never do it. Substack, the service on which Platformer is hosted, long ago took such a step. But so much has changed since then! One, the company has struggled to grow revenues fast enough to raise a Series B round of fundraising at its desired valuation; limiting its revenue opportunities to subscriptions has meant depriving itself of the other, typically larger stream of revenue in every big publisher’s arsenal. Two, Substack got really good at growing free email lists this year with its recommendations feature — but not at converting those free readers to paid.

The company now almost certainly has millions of email addresses at its disposal, but it makes money only from a small fraction of them. The company’s need to grow is too existential, and the solution too obvious, for Substack not to act. By the end of 2023, Substack will have introduced or say it is working on a native advertising solution."