It’s getting such that Facebook users need never buy a meal again. The latest fast-food brand to dangle a free lunch to fulsome Facebook fans is Burger King way up in Norway. For every ten “Like’s” you pepper on the Burger King Norge Facebook page, you get a free Hot Salsa burger. (No, we don’t want to know what they put in the Norwegian salsa). The King follows Domino’s Pizza, which earlier this month created a pizza give-away contest to convince hold-outs to try its new pizza recipe. And, in February, Carl’s Jr. and Hardee’s sought to attract “young, hungry guys” to its new comfort food menu with, you guessed it, a Facebook campaign that involved free comfort food.

But it’s not just the fast-food industry that’s trying to boost its fan base with freebies and discounted goodies. The astute Facebook user this week could score himself a retro 35mm camera, dirt cheap last-minute airfare and free Glee! concert tickets, the latter if he were to stop by Entertainment Weekly’s Facebook page and deliver the “best original Sue Sylvester-inspired put-down.” The instructions, hint, hint continue: “make sure to “Like” us while you’re there!”

In the short life span of social media marketing we’ve learned one thing: free shit rules. If you want to pad your Facebook fan base or Twitter follower ranks, the quickest way to do so is the good old freebie. According to Vanksen, a digital agency that does a back-of-the-envelope calculation on the BK Norway promo, Burger King is buying loyalty (and approval, you might add) on the cheap. Each BK “Like,” it reckons, is valued at $0.29; presumably a Salsa burger costs $2.90. While we’re at it, another agency, Vitrue, calculates the value of a social media fan at a lowly $3.60, a value that it says takes into account just how much “earned media” a brand can expect from the average fan on a social network or blog.

To be sure, all this talk of free comes with a cost, and it’s no doubt why the value of our social media personae, whether or not you agree withVitrue’s calculation, are worth just pennies on the dollar. Advertisers are not cultivating a new generation of brand ambassadors through these promotions, they are turning consumers into mercenaries, dangling freebies in exchange for a kind word, a nod of approval, or recruiting a buddy to join up too.

This gimme-gimme-gimme approach could easily backfire. Case in point: a Dell customer recently took to the computer maker’s IdeaStorm forum, a place where knowledgeable customers suggest product enhancements, to berate the company for its stinginess. “It’s nice knowing about all the deals via Facebook but I’d love to see some Facebook only giveaways,” the customer writes. “Nothing big like a computer (although I certainly wouldn’t complain) but even something like a thumb drive or sunglasses or whatever, just more incentive to check in on Dell’sFacebook page and actually participate in dialouges and discussions.”

The freebie approach of course is a mainstay of the marketer’s playbook. Procter & Gamble and Unilever, to name just two, have used couponing and sampling to great effect to get customers to try new products or to switch from a rival. The somewhat recent invention of the groupon aside, couponing is a private affair between the marketer and the consumer, communicated discreetly in mailers, newspaper or magazine supplements. The aim is to get the consumer to try the product, believing that once you do you’ll be convinced it’s the one for you. The intent of the typical Facebook giveaway, it seems, is to produce as much noise as possible about a new campaign or a new product. Everyone is welcome to comment and grade, even the kind of people whose opinion you’d never seek out. The knowledgeable, trusted brand advocate among us, meanwhile, is drowned out by a cacophony of “I like that!”, “I like that!” If it’s legitimate feedback you seek, you certainly won’t find it among such a sycophantic crowd.

Meanwhile, the big fat freebies continue, enticing us to say something, anything. Today, Cherry Grrl, an online publication dedicated to lesbian issues, announced a new campaign aimed at increasing reader feedback and generating commentary on its site. “Each week, the website will award one lucky reader who has commented on an article or post (or submitted a question to the Dating/Advice columnist, Dr. Oh at AskDrOh@cherrygrrl.com) with a special prize pack,” the press release reads.

What do you think? Is legitimate comment on the brink of being swept aside by prize-seekers and freeloaders? Full disclosure: I have nothing to offer you in exchange for your opinion.

Editor’s Note: Want to learn more about social media best practice? Join our LinkedIn Group and enjoy a great discount on attending the Social Media Conference, June 22.