I was just wondering about this myself. I'm not sure if there's a clear incentive to game salary information. If a company posts a lower-than-real salary, they risk seeming less desirable than their competition to candidates, who may then apply elsewhere. If they post a salary that exceeds what employees are typically paid for the position, candidates will accidentally high-ball when asked about salary expectations.

Falsifying details about employment happiness and health of culture do have clear benefits for deceitful companies however.