Fashion houses all have websites, many offering e-commerce, as well as Twitter, Facebook and Instagram accounts.

Runway shows are now streamed live online, attracting an audience of millions across the planet.

But Marc Jacobs, who recently stepped down from his post at Louis Vuitton to concentrate on his own brand, has become the talk of the town by trading not in dollars but in social media currency.

At the Daisy Marc Jacobs Tweet Shop, fans and fashionistas collect a free perfume sample for every instagram, tweet or any other post that includes the hash tag #MJDaisyChain.

The more creative the posts, the better the prizes. And at the end of the week, the winner gets a Marc Jacobs handbag.

Tommy Hilfiger, another US fashion house giant, says its social media channels provide "personalized access" to millions of fans and consumers.

Twenty local Instagramers have been invited to the label's catwalk show on Monday, one of the biggest of Fashion Week, and given backstage access to record what happens live.

Long gone, Hilfiger says, are the days when it took six months for the catwalk shows to reach the consumer.

"Our digital initiatives underscore the differences between how runway shows used to be done and how they are organized today," Hilfiger says.

Backstage vignettes offer an intimate look at a part of the show previously the preserve only of models.

Rebecca Minkoff, the New York designer who initially made a reputation for producing luxury yet affordable handbags, joined video-sharing app Keek specifically for Fashion Week.

The site allows users to post videos of up to 36 seconds. One shows the arrivals, in the freezing cold, backstage. In another, TV actress AnnaSophia Robb picks out an outfit.

Then there is wearable tech.

Alexander Wang, arguably the biggest draw of the week, unveiled an androgynous futurist show in a Brooklyn warehouse that featured 3-D and heat-activated fabric.

BCBG Max Azria also has "Epiphany Eyewear", their answer to Google Glasses that are equipped with HD video, and sent down the runway on models.

Victoria Beckham, who has wowed the fashion world since making her sophisticated, elegant debut in 2008, has collaborated with Skype in a special Fashion Week project.

The collection of videos, audio clips, Twitter and video interactions highlighted her social media credentials, all the more vital given her previous outsider status.

The male voiceover says social media has forced "a 21st century fashion revolution".

"Once you know the story behind anything, it's more compelling. You can connect with it. Maybe that's what we're doing," adds a member of her team.

-AFP