FORTUNE — I’m fascinated by the story of Francesco Gonzaga, the Marquis of Mantua at the end of the 15th century. For many years, Gonzaga had been viewed as a young, untested leader. Then, he went off to fight for Italy against the French and, depending on whom you talked to, scored an impressive victory at the Battle of Fornovo in 1495. Eager to enhance his reputation as a valiant soldier and liberator throughout northern Italy, Gonzaga commissioned an aging but accomplished artist named Andrea Mantegna to paint him in a most flattering light. This indelible image — now hanging in the Louvre — was seen by thousands of 15th and 16th century visitors to the Renaissance church in Mantua each year, and it helped solidify Gonzaga’s political power far and wide. Mantegna’s ability to change the conversation for Gonzaga has real relevance today; and, as the following piece shows, modern marketers and social network influencers can benefit by joining forces in order to win over the consumers who currently inhabit our brand-hungry world.

The Web is fragmented today with Facebook, Twitter, Tumblr, YouTube, UStream channels, and countless other digital outlets and outposts.

This new Internet mosaic represents a stark — and almost unrecognizable — generational change from the vast media monolith of the mid-1980’s, when 80 million people used to gather in front of their TV sets on Monday nights to watch the Cosby Show on NBC.

And that’s why the old CPM advertising model, where the rate advertisers paid was based on the cost of attracting a thousand viewers or readers, doesn’t work today on the Web — not when the audiences for a typical blog or podcast are so small, even though they’re passionate and committed.

Unfortunately, this presents a real problem for most influencers, because they simply can’t attract enough visitors, readers, or eyeballs to their small sites in order to deliver an audience that makes financial sense to large advertisers.

The challenge goes even deeper for influencers, because, with millions of competitive blogs or sites out there, it’s extremely difficult and time-consuming to get the necessary exposure and attention for profitable growth.

The good news, though, is that marketers really need the influencers and their strong connections to customers.

So, in a world in which the venerable CPM model no longer makes sense, how can the relationships between brand-builders and influencers be structured so that each party benefits?

Let’s take a sample brand like Betty Crocker and sketch out the possibilities.

In the past, digital marketers for Betty Crocker might try to affiliate with a high-profile, top-tier Web channel like the Food Network. Now, perhaps, they might seek to build a meaningful commercial relationship, based on trust, with an Iowa woman we’ll call Christine Carter.

Christine is a passionate expert when it comes to home baking. She also has a blog that other baking enthusiasts around the country love and loyally read. In other words, Christine is an influencer with real sway over her own audience.

After the marketers at Betty Crocker identify Christine, they reach out to her and ask for her expert advice and opinion about various cake recipes. The brand-builders also want to know what Christine thinks about home baking in general.

The relationship between Christine and Betty Crocker is reciprocal. In exchange for her counsel, the Betty Crocker marketers boost Christine’s blog and help drive traffic to it. Maybe with coupons; maybe by sharing early access to new Betty Crocker products; maybe by putting Christine on the Today Show; maybe by paying Christine to attend a trade show; and maybe by taking the content on Christine’s blog and featuring it.

The hope, on Betty Crocker’s end, of course, is that its products will receive good mentions and authentic endorsements on Christine’s avidly read blog. The end users — those who follow and interact with Christine, and those who Betty Crocker covets as customers — benefit from this reciprocal relationship, too. They get even more, and even better, baking content and insights from Christine, who now has the backing of a major brand, Betty Crocker.

Ultimately, Christine might even ask her readers to buy Betty Crocker frosting as a way of showing their appreciation for the support the brand has provided her blog.

This is a 21st century update of the venerable Renaissance patronage model, which allowed members of northern Italy’s powerful elite like Francesco Gonzaga to improve their personal brands among key audiences by commissioning message-laden painting, sculpture or architecture from artists such as Andrea Mantegna, who survived (and thrived) on this largesse.

In today’s version of this process, Christine Carter is a digital da Vinci who is creating the content, and the folks at Betty Crocker are the Medici of modern marketing.

Russ Fradin is the CEO of Dynamic Signal. Dynamic Signal provides white-label technology and services to help brand marketers run social campaigns in collaboration with influential and brand-loyal consumers.Dynamic Signal was founded in 2010, and is composed of digital media veterans from Adify, comScore, Yahoo, RealNetworks, and Google, and is backed by Trinity Ventures, Cox Enterprises, and prominent angel investors.