An article in the New York Times describes the success of Sudoku that was drven by the creator forgetting registering the trademark in the US:
While no one knows how much revenue is generated by the global sudoku business, most agree it has easily topped $250 million over the last two years from an estimated 80 million devotees. The New York Times syndicate provides a variety of logic puzzles, including sudoku, kakuro and others, for newspapers and Web sites around the world.
Nikoli received only a sliver of that money. Mr. Kaji says his private company, with just 20 employees, had annual sales of about $4 million.
Sudoku’s popularity in the United States caught Mr. Kaji by such surprise that he did not try to get the trademark there until it was too late. As a result, Nikoli receives no royalties from sudoku-related sales overseas by other publishers.
In hindsight, though, he now thinks that oversight was a brilliant mistake. The fact that no one controlled sudoku’s intellectual property rights let the game’s popularity grow unfettered, Mr. Kaji says. Nikoli does not plan to trademark other new games, either, in hopes this will also help them take off.
“This openness is more in keeping with Nikoli’s open culture,” said Mr. Kaji, who sat on a sofa in his Tokyo office among pillows adorned with printed faces of racehorses. “We’re prolific because we do it for the love of games, not for the money.”