Possibly, but per [1] it would come down to: "(1) whether the practice injures consumers; (2) whether it violates established public policy; (3) whether it is unethical or unscrupulous."

e.g. it might be deemed "unfair" if you're promoting vaporware to try to slow down sales of a competitor's actual product, and someone could prove consumers suffered "substantial" injury by holding off on purchasing something useful while waiting indefinitely for something else that you had no intention to actually sell. (Proving this would be hard, but I'm sure it's possible.) On the other hand, advertising a joke product—where a reasonable consumer is unharmed because they should have known it's a joke—is almost certainly legal.

See, generally: https://www.ftc.gov/business-guidance/resources/advertising-...

[1] https://www.ftc.gov/legal-library/browse/ftc-policy-statemen...

Depending on which jurisdiction you are in, absolutely.

It could constitute bait advertising. The practice of using fake advertisements to get customers into your store for the purpose of trying to sell them something else.

It's a somewhat well-known startup "hack" https://learningloop.io/plays/spoof-landing-pages

First off, you can't enforce it without making tradeoffs. To some people, the tradeoffs will be acceptable, to others they won't.

One method would be to require a deposit on job postings. Make it costly to post, but return the money when it's taken down - same concept as a bottle deposit.

Depending on the cost, this may or may not unequally impact small businesses - though one could make the cost proportional to the companys employees.

In the U.S., the Federal Trade Commission can prosecute companies for unfair business practices: https://www.ftc.gov/about-ftc/contact

Complaining to your state's Attorney General might also be effective, depending on state law and your AG's priorities with regard to enforcing it.

If you can prove you suffered actual damages due to a fraudulent job posting, you could probably go after the company directly, either as an individual plaintiff or as part of a class action.