When challenged to innovate we’re often tempted by some overzealous instinct to complicate things. But in truth, a good idea doesn’t necessarily have to make your head implode. My latest case in point is the brainchild of Terra, a Mexico-based Internet portal and their ad agency, DDB Mexico.

The campaign cleverly resolves to improve sustainability throughout public parks in Mexico City by offering free Wi-Fi access in exchange for the proper disposal of dog droppings by park-goers on their walks. Terra is currently test driving “Poo Wi-Fi” at ten locations in Mexico City.

Here’s how it works: Each participating park provides a receptacle capable of weighing the discarded trash and supplying timed Internet access based on the weight of the load. The more trash deposited, the longer users can surf what I’d prefer to call “network number two.”

The idea is appealing because, let’s face it, no one’s immune to the ill-fated brown shoe. Parks are public goods, and as such they are inevitably subject to the will of free riders who might choose to dump and dash.  By employing perhaps the most basic of economic principles—that people respond to incentives—Terra can create cleaner, more sustainable parks while visitors enjoy fresh soles and free Wi-Fi.

But what’s to hamper free riders from gaming the system by scrapping nonfecal matter? Nothing, really. In an online interview with Creativity Online, DDB Mexico said it’s a win-win. In either case people are still making an effort to keep the park clean. However, hostesses staff each bin during the day and distribute bags to help dog-walkers focus on the true task at hand.

As of late, we’ve seen some interesting attempts to leverage free Internet as a simple policy tool. You may recall BBH’s “Homeless Hotspots” experiment that debuted at South by Southwest and rewarded donations to the homeless with free Wi-Fi. If BBH’s model made you feel uneasy, you may prefer Terra’s approach. It’s a great example of how incentivizing certain behavior can sometimes prove more effective than pure regulation.