Facebook on Tuesday launched its most ambitious attempt yet to turn its rising popularity into a profitable business by unveiling new features designed to allow advertisers to tap into the “Holy Grail” of word-of-mouth advertising.

Speaking before hundreds of advertisers and media executives in New York, Mark Zuckerberg, Facebook’s 23-year-old founder and chief executive, said Facebook’s new technology represented a new era for advertisers, in which commercials are replaced by messages planted in online conversations between friends.