It’s hard to find a market today that isn’t being impacted by the rapid growth in mobile usage. Smartphone penetration continues to hit new milestones and executives in just about every industry are trying to figure out how to capture the mobile opportunities that increasingly seem within reach.

Just how big are these opportunities?

Former Facebook executive-turned-venture capitalist Matt Cohler believes that mobile ads “will be bigger than the web.” His rationale is straightforward: “it’s a lot more like TV than a web browser ever was.”

Cohler might be right, but advertisers face plenty of mobile challenges. Fat fingers, for instance, are one.

For retailers specifically, mobile has been a mixed bag. According to a new report by Shop.org, retailers are upping their investment in mobile; it was $55,000 last year, the average is $207,000 this year.

But while the vast majority of retailers are making mobile investments, and 60% say they now have a mobile-friendly site, well over half (60%) still aren’t sure about the business objectives for mobile. And, as MediaPost’s Sarah Mahoney details, talent and capital are also sources of concern: 40% of the retailers surveyed indicate that they lack the experience to execute on the mobile opportunity, and nearly as many (36%) aren’t sure they have budget.

The result: despite the fact that only a small minority of retailers are not investing in mobile, the majority which are appear to be, by in large, taking a more cautious approach.

That’s not necessarily a bad thing. As some of the most innovative technology companies in the world have learned, mobile is a tough nut to crack. There are lots of opportunities, lots of challenges and best practices are still being established. In the background is the staggering pace of change as new devices come to market and platforms evolve.

For retailers, the biggest question at this point may not be “How much do we invest?” but rather “Where do we invest?” Mobile strategy doesn’t just involve websites and apps. As Shop.org’s study demonstrates, in-store mobile components, such as electronic receipts and point-of-sale technologies, are likely to be a big piece of the retail mobile puzzle too.