When you talk to a lot of people for a living, sometimes you flat out stumble over things you hadn’t thought much about otherwise. One of the bigger trends to come down the pike lately is the proliferation of Web-based application programming interfaces, or APIs, and how network traffic is growing exponentially through APIs.

Actually, it makes perfect sense. In the Internet sense, an API is the conduit for selectively exposing or extracting discrete information through Web services or other protocols. The API is also the management layer for administering all of those services.

Now think of all the thousands of iPhone apps and how they amalgamate all kinds of Web services. You open your commuter traffic app, it calls on traffic information services, Google maps, a weather forecast and maybe an ad for public transportation. One browser app, many service calls.

Obvious enough, but a lot of information providers are now telling me that a large majority of their network traffic already comes through the API, not through the browser. It’s the power of partnerships, the channel and mashups of all kinds of information.

For example, I’ve been talking to TransUnion about their ConsumerConnect program, which basically sells and re-serves a variety of credit information to consumers through third-party partners, which might be a bank or another financial service provider. The bank creates its own portal to provide the service to its customers, and calls on TransUnion to provide the content.

TransUnion works with a company called Sonoa Systems, which sells software specifically to manage APIs, for visibility, control and load balancing. Scott Regan at Sonoa predicts that 70 to 80 percent of network traffic will consist of Web service calls within a few years. “Five years ago Salesforce.com made themselves the most famous example, saying that 60-70 percent of their traffic was coming through APIs versus bread and butter salesforce apps that everybody uses on their Web browser,” Regan says.

I also brought the topic up on an episode of DM Radio. Raju Vegesna of Web app provider Zoho said 50 percent of the traffic for Zoho’s office suite comes through APIs today, and over the next six to 12 months, he sees that increasing to 80 percent or more.

David Fish of Sybase summed it up pretty well when he said API traffic "is an area that is going to take up a lot of bandwidth in the future."

What does it mean? Well, for starters we don’t have a lot of aggregate numbers to look at. Unlike Omniture or Google Analytics that measure browser traffic, API traffic is pretty much measured at the source, less so in total. Scott Regan at Sonoa says APIs are “kind of like the dark matter of the universe, the stuff you can’t see, because you see all these apps like iPhone and Facebook that use them but we can’t really see the data on them.” Sonoa has a developer tool called apigee that provides self-service analytics for APIs and mashups and figures if thousands of developers with thousands of APIs pick it up, together they could create a large body of information. He wouldn’t mind seeing his company behind such a movement.

But we’re already well into the next generation of the information as a service model and when billion-dollar companies like TransUnion start using it to extend or transform their business model, I want to know more.