The industry also sells huge "building wraps" -- digital or vinyl ads attached to tall buildings -- as well as outdoor ads on bus stops and buses, mobile billboards towed behind vehicles, floating inflatable billboards around marinas, even helicopters lugging flamboyant digital billboards over crowded highways and sporting events.

Billboard companies and their opponents argue endlessly over all aspects of regulations, including the value of the billboards that governments want to remove, whether the new digital ones pose a dangerous distraction for drivers, whether all billboards are protected by the U.S. Constitution's right to freedom of speech -- even whether planting a palm tree that obstructs a billboard is an unconstitutional "taking" of property rights.

Randal Morrison is a San Diego lawyer who has specialized in such battles for more than 10 years, often representing cities that want tougher regulations. He says there's a "gigantic mother lode" of more than 8,000 court cases around the country since the early 1980s -- and the total number of lawsuits is still soaring. The industry's tactics, he adds, include what he calls the "billboard ambush," in which corporations simply keep putting up billboards that violate regulations, daring local governments to take them to court.

After Tacoma, Wash., passed a ban on most billboards in 1997 with a 10-year phase-out, Clear Channel Outdoor -- one of the biggest national billboard corporations -- challenged it in court. The Tacoma City Council and Clear Channel reached a settlement in 2010 allowing dozens of new digital billboards in exchange for the removal of some traditional billboards, but residents revolted, so last August the City Council passed an ordinance that bans digitals and requires the company to take down 190 billboards. Clear Channel says the city should pay it $75 million, the alleged value of the billboards in question. That court battle is still ongoing.

In Rapid City, S.D., more than 65 percent of the voters approved two ballot measures last June, banning digital billboards and imposing new limits on traditional billboards. Another giant national billboard corporation, Lamar Advertising, is fighting those regulations in court. Meanwhile, in Oregon, which had some of the nation's toughest regulations, the Oregon Legislature decided last year that some conventional billboards can be converted to digital.

The anti-billboard crusaders are seldom well funded. If they work in local government, their budgets for court battles are tight. Outside government, they're a loose movement of small nonprofit groups, such as Scenic America (based in Washington, D.C., with affiliates in some states), Blightfighters (a new small national group), neighborhood groups and determined individuals. There's an "imbalance of power," says Mary Tracy, president of Scenic America. The billboard corporations are "bullies -- most of the time the municipality gives up."

Mark Mayer, 63, Arizona's leading crusader for more than 15 years, drives a 1991 Oldsmobile with more than 185,000 miles on it. He used to be a leader of Tucson neighborhood groups as well as chair of the City of Tucson Planning Commission, and now he serves on the board of Scenic Arizona, a Scenic America affiliate that has no paid staff. He's been instrumental in some major victories: After a 1970 Life Magazine story called Tucson's billboard-infested Speedway Boulevard "the ugliest street in America," the Tucson City Council and ballot-measure voters passed regulations in the 1980s that made it harder to install new billboards and called for removal of many existing ones. Billboard corporations persuaded the Arizona Legislature to override Tucson's regulations, but eventually Tucson prevailed in court on the key issues. More than 500 billboards in metro Tucson have been dismantled, including 30 last year, leaving a total of about 390, and there are no digital billboards in the city.

Scenic Arizona and neighborhood groups in metro Phoenix achieved a dramatic statewide victory last November when they convinced the Arizona Court of Appeals that digital billboards on federal and state highways violate the 1970 Arizona Highway Beautification Act's prohibition of "intermittent" lighting on signs. That ruling might halt the push for more digitals in metro Phoenix. Even though some of the nicer Phoenix suburbs have banned billboards for decades, the entire sprawling metro area has more than 1,500, including about 40 digitals. The Phoenix City Council apparently expects the industry to win its case in the Arizona Supreme Court or by lobbying the Legislature to amend state law to allow digitals; just a few weeks after the appeals court ruling, the Phoenix City Council voted 5-4 in favor of an ordinance that allows digitals with only a few restrictions. Now, Scenic Arizona and neighborhood groups, organized as Save Phoenix Views, are circulating petitions for a ballot measure that would ban all new billboards, including digitals. Jim Mapstead, a 60-year-old perennial gadfly who runs a small sign and engraving business and serves as volunteer chairman of Save Phoenix Views, told the Arizona Republic, "I don't know if people understand the significance of what we're going through right now. The new ordinance represents a big shift in the aesthetics of this city."

In Los Angeles, Dennis Hathaway, 69, who retired from a career in the construction industry -- he began as carpenter and worked his way up to become the manager of affordable housing projects -- is the volunteer head of the leading local anti-billboards group, the Coalition to Ban Billboard Blight. That group also has no paid staff, but its few dozen active volunteers are engaged in an epic battle with corporations that have more than 6,000 billboards within city limits. In 2002, the L.A. City Council basically banned new traditional billboards and any modifications of existing ones, which arguably includes conversions to digital. But there were loopholes, and billboard corporations filed more than 20 lawsuits against the regulations. Some corporations simply ignored the ban and put up new billboards, including digitals. In 2006, then-City Attorney Rocky Delgadillo cut a deal with the biggest corporations, allowing them to convert 840 billboards to digital; about 100 have gone digital. Hathaway thought the deal was illegal and waged a guerilla campaign against it, identifying billboards that violate regulations. Eventually, the city won more court cases and passed more regulations. Recently, City Attorney Carmen Trutanich, elected in 2009, has put together a team to enforce the removal of hundreds of the illegal billboards, even filing misdemeanor criminal charges against some scofflaws and collecting more than $7 million in fines.

Now, the Los Angeles City Council is drafting a new ordinance that might have some tougher regulations, but there's "major political pressure from companies to seriously weaken it," Hathaway says. In all three key public hearings since last July, "the room has been filled with lobbyists for sign companies and developers and other business interests -- and that's just in public. There's also an immense amount of lobbying behind the scenes." Since the current regulations have a loophole allowing digital billboards in designated sign districts, there's also a "land rush," with developers proposing 16 new sign districts, "trying to create new little Las Vegases here," Hathaway says. The City Council is even considering allowing billboards in the zoo and in 16 city parks. In all, Hathaway adds, billboard corporations have donated millions of dollars in the last 10 years to city politicians, including the 2006 deal-maker, Delgadillo.

"I'm not anti-advertising -- it's important to our consumer-oriented economy," Hathaway says. "But there's a fundamental difference with outdoor advertising, because you can't ignore it, it's in your face. A public space should be about promoting values of democracy -- diversity and freedom of discourse, everyone having an equal voice and different opinions can be aired, instead of corporate values and the monoculture of one-way communication of the sales pitch. In a very fundamental way that's more important to me than whether a billboard is ugly -- there are profound implications for the urban environment."

"The idea that you can do advertising in any space, on any surface, where there might be people, is reaching new levels never reached before. Advertisers are thinking of ever-grander scale," Mayer says. "That's scary."