This past weekend, biotech giant Monsanto paid bloggers $150 each to attend “an intimate and interactive panel” with “two female farmers and a team from Monsanto.” The strictly invitation-only three-hour brunch, which took place on the heels of the BlogHer Conference, promised bloggers a chance to learn about “where your food comes from” and to hear about the “impact growing food has on the environment, and how farmers are using fewer resources to feed a growing population.” Though the invitation from BlogHer explicitly stated, “No blog posts or social media posts expected,” the event was clearly designed to influence the opinions — and the writing — of a key influencer: the mommy blogger.

Another invite-only event in August will bring bloggers to a Monsanto facility in Northern California for a tour of its fields and research labs. Again, while no media coverage is expected, the unspoken goal is clear.

Stealth marketing techniques, such as these by Monsanto, reveal how the food industry — from biotech behemoths to fast-food peddlers — is working surreptitiously to shape public opinion about biotechnology, industrialized farming and junk food.

We’ve come a long way from Don Draper’s whisky-infused ad concepts meant for old-style print publications. As our media landscape has changed, Big Ag has changed along with it, devising marketing to take advantage of this new terrain and influence the people and platforms — not just journalists and newspapers — that shape our understanding of farming and the health impacts of biotechnology and junk food.

Sean Timberlake, who has been blogging for nearly a decade, characterized industry’s move into the social media space as “sweeping and vast.” He explained that back when he started out, “I don’t think the Monsantos of the world understood what blogs were — or cared,” but now, “companies develop entire budget lines for social media programs. They build it into their whole ad budget.” Ad networks such as BlogHer and Federated — two of the biggest — facilitate companies’ advertising and outreach on blogs by aggregating blogs to sell as a bigger package. These networks, Timberlake explained, “can be leveraged and used as a bullhorn for their marketing.”

Sure, PR is an old game, but Big Ag is giving the age-old techniques of shaping public opinion a new, sneakier spin. Much of today’s marketing happens behind the scenes and off the printed page — on the Web pages of blogs, on Twitter feeds and Facebook pages, through sponsored content and industry-funded webisodes and on the stages of big-ideas festivals.

Monsanto is not the only food company engaging with the blogosphere. Mommy bloggers are the food industry’s newest nontraditional ally. McDonald’s has been wooing them aggressively too, offering sweepstakes in partnership with BlogHer for the company’s Listening Tour Luncheon, an exclusive event with the head of McDonald’s USA — framed as a two-way conversation about nutrition, but more likely a gambit to garner the support of a powerful group of influencers. And in Canada, McDonald’s offers All-Access Mom, behind-the-scenes tours of the company’s inner workings.