“I celebrate myself, and sing myself,” wrote Walt Whitman, America’s great bard of self-promotion. As the world goes ever more digital, quite a few businesses are adopting that philosophy — hiring a veritable chorus of touts to sing their nonexistent praises and lure in customers.

New York regulators will announce on Monday the most comprehensive crackdown to date on deceptive reviews on the Internet. Agreements have been reached with 19 companies to cease their misleading practices and pay a total of $350,000 in penalties.

The yearlong investigation encompassed companies that create fake reviews as well as the clients that buy them. Among those signing the agreements are a charter bus operator, a teeth-whitening service, a laser hair-removal chain and an adult entertainment club. Also signing are several reputation-enhancement firms that place fraudulent reviews on sites like Google, Yelp, Citysearch and Yahoo.

A phony review of a restaurant may lead to a bad meal, which is disappointing. But the investigation uncovered a wide range of services buying fake reviews that could do more permanent damage: dentists, lawyers, even an ultrasound clinic.