There are plenty of examples where bloggers, celebrities and sports people will post sponsored tweets for brands or companies they are representing.

The reward is usually megabucks or a free toy to keep when endorsing whatever the product is in question.

Kellogg’s has done away with the guessing about what is sponsored and what is genuine by opening a pop-up shop in London’s Soho area where people can buy their new savory crisps. The price for the snack? One of your own tweets.

Yes, I went to take a look. No, I am not endorsing Kellogg’s. Yes, I sent a tweet to see how it all works and they offered me some free crisps.

It’s an interesting proposition that connects the real world with our lives online. People who go into the shop get to try the crisps and if they want to take some away, they spread the word via Twitter about what they are up to.

The Kellogg’s examples of tweets on a ‘menu’ in the shop included the hashtags #tweetshop and #spons. The first is the one where they can track who tweeted and the second is making sure they don’t upset the Advertising Standards Authority which likes to see clearly when Tweets have been sponsored.

Of course, it is a guide – or maybe what would be most desirable in a tweet for the product. Naturally people who visited the shop said nothing like the phrases in the picture above and they often didn’t add #spons. But then there’s a difference between a celebrity influencing a large audience and your friends wondering what you’re hashtagging about.  Or maybe that’s still a grey area in social media advertising law.

The exercise certainly has been attracting attention and no doubt the event (which runs until Friday) is an interesting way to explore experiential marketing for companies that have the cash to create a pop-up to put it all in.

We expect to see more variations on this theme. But the deal begs the question, what can you buy for a tweet? A packet of crisps is one thing, but we doubt De Beers will be copying this format any time soon.