KLM is the latest airline to find a way of embracing the FourSquare check-in service - combining it with a bit of detective work to give customers a free gift.
It might send web privacy campaigners scurrying for the terms and conditions, but what KLM is doing appears to be completely above-the-board and is actually a rather neat idea.
KLM takes note of passengers that check-in using FourSquare at various KLM locations around the world, such as departure lounges, baggage claim areas, ticket offices, etc.
Using the freely available information available on FourSquare, such as links to a user's other social networks, the airline's KLM Surprise team trawls through sites such as LinkedIn, Facebook and Twitter to understand more about the person, where they are planning to go next, experiences they have had, what they like doing.
Some passengers are then greeted with a surprise gift, next time they check-in at an airport gate or luggage drop.
Not wanting to miss out on pushing the project further, each recipient is snapped for the KLM Surprise Facebook page and a short story about why they received the gift is given.

"At the gate we surprised Saskia with a few pounds of Italian flavour. So she can make the best Italian dishes. We also gave her a handfull of coins to test her own luck when she's at the Trevi Fountain."
Or...

"We surprised Ewald at the gate before he had to leave for a congres in Caïro. The congres was all about social media and 'searching for new connections'. We thought it would be an appropiate idea to give him a cinema ticket so he can visit The Social Network movie."
This is not the first time KLM has tried to use social media for something other than flinging offers or discounts around the ether. In April this year the company started a luggage promotion via its Facebook page.
On a dedicated channel on the page, users could incorporate pictures from their Facebook profiles to create personalised, plastic luggage tags to be sent to passengers.
Of course, promotions such as the FourSquare initiative may have their limitations or attract mischief-makers. Expect to see plenty of "I really wish I could see my brother-in-law in Australia", etc, etc in the coming weeks.
British Airways recently ran a FourSquare promo to reward customers with a free cup of coffee when they checked in at a BA booth in Grand Central Terminal in New York.
NB: Hat-tip - TheNextWeb.