It appears that the tweet’s value is on the rise.

With brands scrapping for attention on social media and consumers increasingly expecting rewards for paying attention and playing along, a few companies recently engaged passersby by exchanging products for the price of a shout-out on Twitter or Facebook.

Kellogg’s handed out boxes of its new cereal at a pop-up All-Bran Tweet Shop in downtown Toronto’s Eaton Centre last month. To get a box, consumers tweeted with the hashtag #AllBranTweetShop or wrote a Facebook post on the brand’s wall. The shop was part of a larger media strategy led by Starcom, with TV and online advertising by Leo Burnett, sampling by Inventa and PR by Strategic Objectives.

Initial feedback from visitors to the shop was positive, says Andrew Loucks, VP Marketing, Kellogg Canada. In addition to tweeting the hashtag, many users added positive product reviews.

A  nearly identical Kellogg’s campaign in London, England for the company’s Special K Cracker Chips, generated 2,800 media mentions, the majority from customers visiting the shop, Loucks says. More than 72 million people were reached through that program.

In February, Hot Wheels and Chevrolet Canada, working with TrojanOne, placed a retrofitted vending machine on the show floor of the Canadian International AutoShow in Toronto. Passersby tweeted @HotwheelsCanada with the hashtag #ChevyCIAs to get a pint-sized version of the Chevy Camaro. More than 1,800 cars were delivered through the vending machine over the run of the show, according to Danielle Minard, manager of consumer engagement at TrojanOne.

Liz Crawford, VP strategy and insights at Marketing Drive, expects more companies will develop offers to earn social currency – a tweet, a Facebook posting or a “like” – from people rather than real money.

“The value exchange mechanism is the key to driving engagement in the digital world and successful marketing of the future,” says Crawford, author of The Shopper Economy.

“I do believe that activating consumers’ social networks to create buzz is here to stay,” she adds. “These mechanisms are an important part of the marketer’s arsenal to get the word out.”