Kaufman likens the current state of DOH to the Web, circa 1995. "That's the year I stopped having to explain to people what the Web was," he says. It was when AOL, Salon and Slate were being hailed as the future. And while they are still here, the online world has taken some unexpected twists and turns.

"When a new interactive platform with its own behaviors comes along," says Kaufman, "it destabilizes the existing economics for the parent medium." He points to recent projections from Carmel Group that DOH is expected to grow an estimated $2.5 billion in revenue by 2010. And it's an additive medium; it doesn't take dollars away from anywhere; it just generates new (and by some predictions, limitless) possibilities.

"Interactive media have the potential to be social, useful and transactional," Kaufman says. And they are also highly measurable -- which is why DOH may run afoul of privacy watchdogs."

Imagine how those who get apoplectic about behavioral targeting will get worked up when they learn of facial recognition. Kaufman calls facial recognition "the most evil cookie." And the name might be fitting; if mobile is DOH's clickthrough, then facial recognition is its evil cookie. The technology could allow the tracking of specific individuals, where they live, work and relax and how much attention they pay to ads. Is it starting to sound like "Minority Report" again?

Remember in the film "Medium Cool" when the crowd outside the 1969 Democratic Convention in Chicago chanted: "The whole world is watching" as the frame zoomed in on a camera lens? Well, we've leaped from that to "The whole world is interactive."

Kaufman says Schematic has proposed interactive out-of-home screens to Blockbuster that could change the company's business model. In this model, touchscreens in malls or train stations aren't merely ads for the store -- they are the actual store, allowing passersby to browse Blockbuster's entire collection and download what they want to a mobile device right there.

"We're extremely excited about the creative possibilities that come out of DOH," Kaufman says. "But we're not there yet. People are still a little afraid of it." Developers still need to include cues to the user that the screen can be played with, the way display ads on Web pages once needed to instruct "click here."

Kaufman recounted an instance where the Schematic team, which had been developing touchscreens, walked into a client's office for a meeting. They saw a big back-lit screen in the lobby, and they went straight up to it and started tapping -- to no avail.

"We'll get to a place where people walk up to a screen and assume they can touch it," he says. "It's hard to imagine how people are going to be using Digital Out-of-Home a few years from now."