Definitions aren't that important. What's important is figuring out what contributes to society and what ends up just looting our attention.

A good (but not perfect) guideline is that voluntary transactions are beneficial to both parties because otherwise they wouldn't participate, and transactions where one party doesn't actively agree to it are often bad because the other party has no incentive to make it otherwise.

That's why I focused on whether the viewer actually wants it. If I seek it out, then it's useful or at least entertaining. If I don't, then it's probably a net negative for me.

I agree that that the criteria you gave is probably more relevant for the issue at hand, sure.

And, while definitions may not be super important (as you say), and while it is often fine to redefine a word within some context, I do think the definition I gave is probably closer to how people usually use the word “advertisement”.

My inclination is to stick on an adjective though, and refer to, say, “unwanted ads”, rather than say that the ads in a classified section “aren’t ads”.