Philadelphia fans are notorious for letting their teams know exactly how they feel, whether it's by pelting Santa with snowballs or climbing Crisco-covered street poles.

Now there's a less dangerous way for fans to give their feedback during Flyers and 76ers games.

The Wells Fargo Center has installed 75 "HappyOrNot" machines to allow fans to rate restrooms, retail locations, and concession stands. The devices have just four buttons – ranging from dark green and very smiley to bright red and really frowny – and collect volumes of anonymous data.

That data can help spot a messy restroom, allowing staff to quickly clean it. The information can also show trends, such as popular concession stands or a day of the week when customer satisfaction consistently drops off.

"It's finding our holes, finding where to allocate our resources," said Ben Schlegel, the center's director of events. "It's just giving us data to make those more-educated decisions."

HappyOrNot, founded in Finland in 2009, has devices in thousands of airports, stores, and restaurants in 117 countries, according to the company's website. Levi's Stadium, home of the San Francisco 49ers, uses them. The Wells Fargo Center is the first NBA/NHL arena in the country to install the machines, as part of a multi-year, $250 million renovation project, management said.

HappyOrNot says the simplicity and anonymity of the terminals generate higher response rates than traditional customer surveys, which may ask consumers to answer several questions or divulge personal information. The company's Smiley Terminal poses a single question — for example, "How was your concession experience today?" — with four smiley or frowny buttons. The company claims the machines collect responses from 20 percent or more of foot traffic at a given location, compared with 2 percent for the traditional survey.

"We simply get just dramatic amounts more of data, because it's just so much more accessible," said Brad Winney, president and general manager of HappyOrNot's Americas division. "The key is, we get it on a continuous basis. So there's no latency in terms of waiting for a survey to be filled out."

That instant feedback on smart phones has helped the center address issues as they occur since it started using the devices during the Elton John concert on Sept. 11, said Mandy Bauer, the arena's guest experience manager. During a recent Flyers game, staff got an alert on a men's bathroom because 30 percent of the responses were negative in a 15-minute time frame.

"All the managers, the department heads, we're all in this app, and we can communicate to each other within the app, and then mark that [the issue] has been fixed," Bauer said.

HappyOrNot's apps format the data into bar graphs and pie charts showing how happy (or not) its customers are during certain hours or days. For example, the "Happy Index" at the Wells Fargo Center was higher during last week's Flyers vs. Islanders preseason game than it was during a Childish Gambino show the next day.

Experts said businesses should be cautious when interpreting the data. Paul Pavlou, a marketing and management information systems professor at Temple University's Fox School of Business, said such surveys can have biased results because the most happy or upset customers are the most likely to respond.

"You're getting the extreme cases. You don't get the moderate cases that usually represent the majority of the people," he said. If businesses aren't careful in analyzing the data, they could make long-term decisions that don't reflect the experiences of most customers, he added.

The anonymity of the HappyOrNot data also prevents companies from knowing if they're satisfying their most important customers, said Peter Fader, a marketing professor at the University of Pennsylvania's Wharton School. For example, feedback from season-ticket holders would be more valuable than responses from fans who rarely attend games.

"Looking at the overall happiness meter isn't necessarily a good indication of how we're doing with the right customers," Fader said. "These kinds of measures taken in a vacuum without a connection to who is the person pressing the button might not be indicative of the health of the customer base."

The HappyOrNot machines use delay filters to prevent one customer from skewing the data by striking a button several times, a feature that could be useful if the Flyers get shut out this season.

"We have an array of filters that essentially allow you to essentially de-noise the data, whether that's kids pressing the buttons or angry fans just hammering away at the system," said Winney.