I assume advertising isn't intended to be the primary revenue stream, but rather a mechanism to monetize the number of free users. The real risk, as you rightly point out, is the loss of users. If the return on investment isn't achieved through subscriptions, diversification will be mandatory, not optional, as they're currently considering.

Ads not only generate direct revenue but also serve as a metric for understanding end-user needs. However, I agree that the biggest threat is the negative public reaction. They risk losing their "premium tool" image for a revenue stream that, according to your data, is minimal. Now, the important and crucial question, which you also raise in your post: Is the reputational risk worth it with such a small margin? Only time will tell; we'll see how it evolves and what impact it will have on the competition.

That's a very interesting question. From my point of view, I'd like to see where all this AI stuff is headed.