Can't businesses opt-out of Yelp by sending a cease and desist letter or eventually suing Yelp?
Restaurants can't opt-out because they would no longer be discoverable on the internet, but a real estate agent should be able to opt-out of Yelp and still be reasonably successful.
What exactly would Yelp be ceasing and desisting here? Surely things like the name, location and contact info for a business are public information that can be freely reproduced. Everything else on Yelp (primarily user reviews/photos) aren't the property of the business in the first place.
If anything I'd expect the example in GP's case to be a rare instance where even US defamation law might be helpful to the landlord. I don't see that extending to businesses in general though.
Restaurants can't opt-out because they would no longer be discoverable on the internet, but a real estate agent should be able to opt-out of Yelp and still be reasonably successful.