The payback for carriers? Increased data traffic on their then newly-built 3G networks.

"But with data going flat rate everywhere," explains ScanBuy CEO Jonathan Bulkeley, "increasing ARPU [average revenue per user] from consumers is not where the real upside is for carriers anymore."

Instead, ScanBuy hopes to "monetize the transaction" - and generate revenue in a much more traditional way, from advertisers. It will then share revenues with carriers and/or, in some markets, device manufacturers. In Japan, advertisers basically get a free ride.

In the ScanBuy architecture, there are three components: the code itself and the scanning software on the device - as in the Japanese model - plus, in the middle, a server that registers codes, receives requests from users' devices, connects them to advertisers' websites (or performs other encoded actions) and records the interaction.

The codes are only useable when registered with ScanBuy. The company has exclusive license to the EZcode technology from the Swiss university that developed it. While it is currently distributing the ScanLife device software online, it expects carrier or manufacturer partners will preload it on devices in future.

There will be different software for different regions - similar to DVD player firmware. The North American software, for example, will only read North American-registered codes.

ScanBuy expects advertisers will pay three to five cents per click - per website visit from a ScanLife user. The pitch is that advertisers don't just get exposure to qualified consumers for their messages, they also get detailed location- and demographic-specific reporting on those consumers.

"Seventy percent of the value [to advertisers] is in the reporting," Bulkeley says. "And 30% is in simplifying the interaction for the consumer."

"So we bill Coke [if The Coca-Cola Company were an advertiser], and we share the revenues with the carrier. That's the model for us in the U.S. The carriers control what software goes [on the device] here."

It gets more complicated in markets where carriers don't have as tight control over devices. Where device manufacturers sell directly to consumers - and agree to pre-load the ScanLife software on their devices - they get a share as well.

Will this model work?

The reporting ScanBuy promises may well have value to advertisers. But the ScanBuy strategy seems predicated on continuing tight control of devices by carriers and manufacturers, making it possible for them - and ScanBuy - to control this market. And on mass distribution of software creating a critical mass of users in short order.

Both assumptions seem open to question.

As Bulkeley points out, right now, only 5% of phones in the U.S. market can use free, downloadable QR code scanning software. But that percentage is bound to increase, possibly rapidly, as smartphones and PDA phones capture a larger share of the market here.

Will some advertisers question why they should pay ScanBuy when they could distribute their own QR codes and reach a growing audience of users and get at least some of the same benefits for nothing?

In the final part of this series, we'll look at possible timelines for the spread of QR codes in North America - or EZcodes. And we'll consider another question: is this all there is to mobile barcode reading? Is it just another advertising mechanism? We think not.