Alberto E. Rodriguez / WireImage Skateboarder Tony Hawk arrives at a post-Grammy event in Hollywood on Feb. 10, 2012.

There’s no mystery as to why companies give away swag during the Oscars to people in the movie business. The possibility that a celebrity will Tweet about the product or perhaps be photographed with it more than offsets the cost of giving goods away. The same concept explains why high-profile athletes are now welcome to eat free burritos for life.

A Sports Business Daily story on the trend notes that in marketing circles, the practice of strategically giving away merchandise is known as “celebrity seeding.” Among pro athletes, the Chipotle fast-casual burrito chain is tops for freebies. Here’s how the scenario plays out:

Chipotle waits for well-known people to express an affinity for the company’s food either privately or publicly, and then sends them a card that gives them a free burrito a day. The company asks for nothing in return for the favor, but many high-profile athletes have taken to social media to sing the company’s praises after receiving one.

That’s exactly what USA soccer star Abby Wambach did last fall, Tweeting “Happiest day ever” after receiving her free-burritos-for-life card. Skateboarder Tony Hawk, the NBA’s Mario Chalmers and Drew Gooden, and pro lacrosse player Paul Rabil are among the other athletes who can flash a personalized Chipotle card in exchange for one free burrito daily until their final days.

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The latest big-time athlete to receive the free-burrito card is Washington Nationals All-Star outfielder Bryce Harper, who Tweeted this week words of thanks to Chipotle. “The best thing ever! I really appreciate it!” Harper’s message reads.

That’s some endorsement for Chipotle. And it didn’t have to spend millions of dollars or deal with Harper’s agent or bother making a commercial or anything. All Chipotle had to do was send Harper a card, good for one free burrito daily. If Harper took advantage of the card twice a week, that’d amount to maybe $600 annually in free burritos. That’s retail. Chipotle’s actual costs are much less. In other words, this seems like a pretty amazing deal—for Chipotle.

All sorts of brands try to tie themselves to professional athletes. But pairing up with superstar athletes especially makes sense for Chipotle since its image revolves around food that’s healthy and fresh (and often organic and locally grown), at least compared to typical chain-restaurant fare.

What’s more, because no money appears to be trading hands, consumers are led to believe that these athletes are genuinely excited to get their hands on Chipotle’s food. This isn’t necessarily the impression one gets when watching an NBA star in a TV commercial smile awkwardly while holding a carefully manicured Big Mac. Compared to TV ads, “Word of mouth is something that builds a lot stronger and it’s not as artificial,” Chipotle social media manager Joe Stupp told Sports Business Daily. “We think our food sells itself, and that’s one of the things that enables our word-of-mouth marketing.”

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But as these stealth word-of-mouth campaigns spread, should we start questioning whether brand mentions by athletes and other celebrities come with strings attached? The restaurant blog Inside Scoop SF recently noted that San Francisco Giants Brandon Belt has repeatedly discussed on Twitter and radio interviews his love for two particular restaurant chains: Olive Garden and Five Guys Burgers and Fries.

There’s no reason to believe that Belt doesn’t love their food. But perhaps he’s also fishing around for free food from the restaurants. For all we know, he could be getting meals comped there already, and that’d make sense. He’s giving them tons of free advertising, after all.