The vacation-rental site has been under scrutiny in Portland and other U.S. cities for its effect on neighborhoods, its impact on local housing markets and the fairness of offering de facto hotels that don't follow the same rules as the traditional lodging industry.

Airbnb is under pressure from the city of Portland to make sure its hosts are following city rules, which include getting a license to operate and submitting to fire and safety inspections. About 94 percent are not (Murmurs, WW, Feb. 25, 2015). As WW has also reported, many Airbnb rentals appear to violate city rules requiring hosts to live in the units that they rent out ("Hotel California,” WW, Feb. 18, 2015). 

With more than 1 million listings worldwide, Airbnb's vast database provides a window into its markets, its customers and the people renting out their homes. Yet the company has been loath to cough up information on hosts who aren't following the rules.

In Brooklyn, technologist Murray Cox decided to meet Airbnb's reticence in his own city with a wily hack. He had wondered about the impact of Airbnb on his neighborhood, Bedford-Stuyvesant, but couldn't get the answers he wanted from the company's website.

Cox wrote a script to "scrape" thousands of Airbnb's New York City listings from the company's website. With designer John Morris, Cox built an interactive site showing every Airbnb rental in the city. The result was a sea of dots representing Airbnb rentals—and according to Cox, more than half might be in violation of New York's rules.

"Airbnb is not truly acknowledging how people are using their service or the negative impact on housing and the community," Cox says.

WW asked Cox to adapt his project for Portland. Cox scraped Portland's 1,959 listings as of March 1 and has published the results at insideairbnb.com/portland.

The site produces maps to show where rentals are in each neighborhood, what type they are (complete homes, single rooms, etc.), general availability and average rates. Users can click on the dots to learn about individual hosts and their properties.

Cox's research confirms what WW has already reported: Airbnb appears to be rife with rule breakers. Using the site's data, Cox found that 75 percent of hosts make their entire homes or apartments available for at least half the year. That appears to violate the city rule requiring hosts live in the homes they offer for rent at least nine months out of the year.

Airbnb wouldn't answer questions about Cox's findings. "We don't comment on public scrapes of our information, because, like here, they use inaccurate information to make misleading assumptions about our community," says company spokesman Christopher Nulty.

Portland officials still won't commit to a full-on enforcement of its rental rules. Dana Haynes, spokesman for Mayor Charlie Hales, says the city has issued warning letters but has yet to levy fines. "We don't really micromanage the bureaus to the degree people think," Haynes says.

Cox says he had been approached by housing advocates around the world and is considering expanding Inside Airbnb to other cities.

"I hope I can contribute to the debate," he says, "by providing some facts and invite Airbnb to be open and provide more."