Most VCs lump marketplaces into one bucket. Rob Mihalko has spent a career proving why that's a mistake. He grew Ariba Network, a B2B marketplace, from zero to $400 million, the platform that today carries over six trillion dollars in commerce a year as the SAP Business Network. He's had three exits to SAP, Microsoft, and Disney, advised or invested in more than 50 marketplaces, and teaches the digital marketplaces course at Stanford Continuing Studies. Now he runs Spectus Ventures, a seed-stage fund backing US founders building digital marketplaces and business networks. He sat down with Connor Sattely of Decile Group to explain why marketplaces are a specialty, not a category.

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Ask Rob to define a marketplace and he starts with a correction. "Marketplaces have existed in the world for, you know, literally thousands of years, starting with the early spice bazaars," he says. What changed is the medium. Digital marketplaces let "multiple parties come together, meet each other, interact, and ultimately transact," and unlike a straight e-retailer they're open platforms: "as long as you meet the criteria that's set by the marketplace operator, you can participate."

That openness is why lumping them together misses the point. People use marketplaces constantly without noticing. "If you ever took an online course on Coursera, you're using a marketplace. If you booked a restaurant at Open Table, you've used a marketplace. If you look for and found a parking spot using Spot Hero, that is using the marketplace business model." Each is a different business with different dynamics. A single taxonomy can't explain a category this internally varied, and that variance is exactly where a specialist finds edge.

Rob could plausibly go build the next great marketplace himself. He chose to fund them instead. After a career spanning consumer software, B2B enterprise SaaS, and marketplaces, where he led product, led marketing, and served as a general manager growing businesses from scratch up to scale at companies like Microsoft and SAP, he wanted broader reach. "I wanted to see if I could help other companies become successful, sort of learn from the things that worked well when we were building marketplaces, things that didn't work so well," he says. "If I can add value to the industry, I thought doing it in the form of investing would be the way to do that." His attraction to network-effect businesses runs deep. He started his career in the airline industry, building transportation and logistics networks, long before software.

Spectus has a mission Rob states plainly: "to invest in the next generation of leaders in the marketplace economy." That's a term the fund coined for the slice of the global economy powered by digital marketplaces and business networks, which their research pegs at roughly twelve trillion dollars in commerce. It's massive, and Rob argues it's still wide open. New technologies keep unlocking new marketplace designs, and even in categories with incumbents, "there's new entrants that come in with a slightly different marketplace design, slightly different business model that can prove superior."

The verticals he finds most interesting: services ("inherently complex," so marketplaces can standardize buying, selling, and delivery), the experience economy and travel, the creator economy, B2B, and healthcare, which he calls "a massive industry that is underserved by marketplaces."

Rob's sweet spot is specific. "I tend to work with marketplaces that have a product in the market, but they haven't quite achieved product market fit and they're not quite ready for their scale and growth investment." In an era where anyone can spin up a marketplace with a few prompts, he leans on hard-won pattern recognition. First, is the plumbing working: "what percentage of buyers who are interested in buying can find a supplier or a vendor to work with and can complete a transaction." Then, is growth turning organic: are they "starting to attract people outside of that sphere," getting word of mouth and network effects rather than only paid acquisition. He checks basic unit economics and customer acquisition cost, not to over-index on them early, but to make sure they're "in the right zone." And he wants the revenue model out early: "some general willingness to pay" that proves there's a real business underneath.

Marketplaces don't produce small outcomes when they work. "If you just take the mobile transportation industry, Airbnb and Lyft, they essentially took an extremely inefficient industry and made it more efficient," Rob says, and both are now public companies worth tens of billions. He points to ServiceTitan, DoorDash, and Instacart as recent large IPOs. "When marketplaces become successful, they literally can transform industries, they can expand industries, and therefore create tons of value." As an early-stage investor, that's the test he applies: can this company become "a standalone publicly traded company sort of owning or even transforming a category they're in."

Rob is selling more than capital, and his LPs know it. Two groups gravitate to Spectus. First, "executives or former managers who've worked in marketplace businesses" who understand the model's intricacies and want an investor who does too. Second, family offices and high net worth individuals who appreciate marketplaces from their own lives or portfolios. What draws them is the combination of a defensible asset class, high switching costs, network effects, scale economies, and an investor who has actually built these businesses. Spectus is also assembling a bench of marketplace-expert advisors to plug into portfolio companies, and Rob brings the frameworks from his Stanford course directly to founders. The feedback from the companies he's backed early is consistent: he complements their vertical-specific investors with horizontal marketplace expertise. "I bring a unique set of skills to the table from an investing standpoint."

Spectus Ventures is a specialist bet for LPs who want exposure to the marketplace economy through someone who has built inside it, exited from it, and teaches it. For founders with a marketplace in market but not yet at product-market fit, Rob offers the rare early-stage investor who has walked the exact path, knows where the plumbing breaks, and can tell a pilot from a real business. If you're building a digital marketplace or business network, this is the fund that speaks your language.

Learn more about the fund and request access on Decile Access: https://decileaccess.com/funds/Spectus-Ventures

Spectus Ventures is a seed-stage venture fund backing US founders building digital marketplaces and business networks. The fund is led by Rob Mihalko, who grew Ariba Network from zero to $400 million, has had three exits to SAP, Microsoft, and Disney, has advised or invested in more than 50 marketplaces, and teaches the digital marketplaces course at Stanford C

Watch The Full Episode Here: https://www.youtube.com/watch?v=5dsuzM3-HRo ontinuing Studies. Spectus invests in the next generation of leaders in the marketplace economy, backing companies with a product in market that are approaching product-market fit.