Laws limiting outdoor advertising are designed to protect what the 9th U.S. Circuit Court described "as perhaps the state’s most valuable and fragile economic asset — the natural beauty upon which Hawaii’s tourism economy relies."

Max Ashburn, communications director of Scenic America, a Washington, D.C.-based nonprofit, said Hawaii is considered a model in a global battle against the visual blight and commercialization of public spaces associated with outdoor advertising.

"That’s why it’s so disturbing to hear that your city buses could become what are essentially rolling billboards. What happens is that transit systems say, ‘OK, we’re making a little bit of money with the ads on the buses, so how about the bus stops, the benches, even the trains? You get hooked on this advertising revenue and then one day you wake up and realize your city is completely different than it used to be. You’ve lost your sense of place."

Four states — Maine, Vermont, Alaska and Hawaii — and 700 U.S. municipalities ban billboards, and 1,500 communities have prohibited construction of new ones, Ashburn said. That includes Houston, which this year rejected a proposal to sell advertising on the exterior of city buses; its City Council scotched the plan as a violation of the spirit of its anti-billboard law and a step backward in a city that has dismantled 6,000 of the 10,000 billboards that stood in 1980.

International locales are part of the movement: Sao Paulo curtailed billboards in 2007, and Buenos Aires, Argentina, followed suit the next year.

THE OUTDOOR Advertising Association of America categorizes outdoor advertising as billboards, transit advertising, street furniture, and alternatives such as aerial banners. McDonalds Corp., Verizon Communications Inc., JP Morgan Chase & Co., Apple and Metro PCS Communications Inc. were the top advertisers in 2012.

"Billboards look the same whether they are in Mississippi, Missouri or Malaysia," Ashburn said. "Almost nothing destroys the distinctive character of a place faster than a proliferation of signs and billboards."

Not everyone takes that view, of course: towns in Florida and North Carolina have cut down trees to make paid billboards more visible.

Apart from aesthetics, outdoor advertising can impact health: A study out of UCLA this year found that the more outdoor advertisements for fast food and soft drinks there were in a given Census tract, the more likely residents were overweight.

Bottom line, Ashburn advises: "Before Honolulu sells outdoor advertising, think very carefully about what you’ll be giving up."