On hopping Robson Street, the retail heart of downtown Vancouver, shop windows are ablaze with red and white as retailers seek to take advantage of the biggest game in town.

But observers see a fine line between marketing and breaking tough Olympic rules, as the IOC struggles to crush ambush marketers and companies look to tie themselves to the Winter Olympics, without making the line too tight.

Is it clever marketing to tie yourselves to a sport, knowing that people are going to make the mental leap? asked Paul Payack, president and chief word analyst at Texas-based Global Language Monitor, which on Thursday released an index of so-called ambush marketers at the Vancouver Games.

There's never going to be an absence of ambush marketers. It's just a question of how clever you are about it.

The International Olympic Committee (IOC) takes a tough line against what it calls ambush marketing, where companies who have not paid for sponsorship rights seek to tie their products to the Games.

Using the Olympic rings is an obvious no-no, but even linking words gold and medal, or 2010 and Whistler -- site of the Alpine ski events -- breaks Olympic guidelines.

Companies which try to create the false impression that they are an official partner of the Olympic Games, or create a false association with the Olympic Games, are cheating Olympic athletes, Olympic Games' organizers and Olympic fans, the IOC said last week.

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Companies on Payack's ambush list include hip Canadian yoga clothing retailer lululemon athletica (LLL.TO), whose downtown Vancouver store showcases red-and-white mittens with more than a passing similarity to the wildly popular official mitts.

Another is fast food chain Subway, which United States Olympic Committee (USOC) singled out last week as an ambush marketer.

Subway, which denies wrongdoing, features 14-times Olympic swimming champion Michael Phelps in a campaign which USOC believes implies Subway helps sponsor the Olympic team.

But Payack said it was hard to know where to draw the line between ambush marketing and clever business. The IOC does not think it takes much to be an ambush marketer, he said.

Global Language Monitor also tracks new words in the English language, with snowmageddon and snowpocalypse -- from the recent storms on the U.S. Eastern Seaboard -- as some of the latest additions.

Payack said it was too early to say what words might come out of the Vancouver Games. Vonncounter -- from U.S. Alpine skiing gold medalist Lindsey Vonn -- was a possibility.