London - One day, the small espresso shop near the site of the London Games was the "Olympic" cafe. The next day, it was the "Lympic."

So where did the "O" go?

The manager won't say. But it's more than likely the small business became another casualty in the battle against guerrilla marketers - advertisers who try to associate their products with an event without paying to be sponsors.

Protecting the Olympic brand is always a big job, and never more so than this year. Olympic organizers say the increasing sophistication of guerrilla marketers and the rise of social media are putting the five rings under assault in ways barely envisioned a decade ago.

That means action against anyone who infringes the Olympic brand or sponsors' deals - no matter how small.

"There's no question that the rings are instantly recognizable - it's what makes it attractive," said Stephen Greyser, an emeritus professor at Harvard Business School.

He compared the efforts by non-sponsors to athletes trying to find loopholes in the rules against performance-enhancing drugs.

"It becomes an industry," he said.

The International Olympic Committee and London organizers raised more than $2.4 billion from the sale of marketing rights in the four years through the 2008 games in Beijing, providing more than 44 percent of their funding during the period.

The rings are among the world's most recognized symbols. Companies like McDonald's, Coca-Cola and Samsung, which pay as much as $100 million each to be official sponsors during each Olympic cycle, expect organizers to protect their rights.

If others can use the rings and the name "Olympic," why should the big companies pay so much money?

"Without our sponsors, the games simply wouldn't happen," London organizers said in a statement. "They provide funding, products, services and expertise to help us stage the games and with that have purchased exclusivity in their sector."

British lawmakers did their part, passing a law - described as draconian by critics - that gives organizers the power to bar companies from using Olympic trademarks and even certain combinations of words, such as "London 2012," that may infringe on the rights of sponsors.

"Where there are serious or deliberate attempts to ambush the Games ... we will take swift and firm action," London organizers added.

But if the crackdown on guerrilla marketers goes too far, it could anger those attending the games or going about their business in London. Organizers will find it hard to tell people they can't wear their Nike T-shirt into Olympic Stadium because adidas is the sportswear partner.

"It's fine to clamp down on the threat, but where it impacts the individual, it's going to be very difficult for (London organizers) to get it right," said Hugh Tebay, a partner at Sipara, a British law firm that specializes in trademark and branding. "If public reaction is too strong, they'll have to backtrack."

Such worries played out during another big international event, the 2010 World Cup in South Africa. The Bavaria brewing company outfitted some 30 Dutch women in mini-dresses in its eye-popping trademark orange for the Netherlands' opening game against Denmark. When the ringleaders were caught and authorities in Johannesburg threatened jail, Bavaria agreed to refrain from future marketing ambushes until 2022.

Four years earlier at the 2006 World Cup in Germany, the brewery gave fans orange lederhosen. Guards confiscated the Alpine-inspired pants, forcing hundreds of fans to watch a match in their underwear.

Then there are the infamous cases, such as in 1992, when non-sponsor Nike held news conferences with members of the U.S. basketball team. Michael Jordan, who had an endorsement deal with Nike, accepted his gold medal while covering up the logo of the team's official sponsor, Reebok.

Some companies are already flying close to the sun in London.

The British company Virgin, whose interests include airlines, broadband service and holiday travel, has an ad featuring Jamaican gold medal winner Usain Bolt sporting a silver goatee identical to that of company founder Richard Branson. The campaign pushes Virgin's "super fast" broadband service, skirting the rights of BT, the games' official broadband provider.