[adrianba]

That's not quite how it works. In practice, in the US, liability comes not so much from giving a positive or a negative review, but from giving an incomplete one. This is most apparent as a result of giving a positive review and leaving out the bad bits. In this case, you might be liable for the negative consequences of hiring someone based on your positive review.

For an extreme example, see Randi W. v. Muroc Joint Unified School Dist [1]. In that case, the plaintiff sued several school districts for fraudulently or negligently providing positive recommendations for a teacher who ultimately sexually assaulted her. The California state Supreme Court held that the school districts were liable because there was a substantial, foreseeable risk of physical injury to a third-party resulting from the misrepresentations.

For this reason, it is common practice for businesses to decline to provide a review and instead simply confirm a prior employment relationship and the dates of the employment.

[1] https://law.justia.com/cases/california/supreme-court/4th/14...

[CheezeIt]

That’s a great point, but at least as far as negative references go, you have libel/slander law with robust free speech protections. It’s nothing like Europe.