Momentum for smart cities projects, which has been fed by big promises from industry and big hopes in government, is slowing down in the face of a wave of public skepticism.

Driving the news: Alphabet-owned Sidewalk Labs, which has proposed a futuristic smart-city development for Toronto's waterfront, has pledged not to sell personal data collected at the project or use it for advertising to assuage privacy concerns.

Instead, if the plan is approved, local government entities will take the lead on managing data.

Context: "The U.S. has a general optimism that technology can make our lives easier if used in right way. But that’s countered by mistrust of intentions or capabilities of state and local governments," said Todd Daubert, chair of the communication and technology practice at Dentons, a law firm that works on smart city developments.

There's also distrust of the tech companies that see cities as a huge market for selling their data-guzzling tools.

Sidewalk Labs originally proposed an independent "urban data trust" to manage the data collected in Toronto's Quayside project.

But residents and city officials were uneasy about how it would work, and lack of clarity around Sidewalk's business model spurred opposition.

The company has now pledged to minimize data collection and to build only about 25% of the technology systems used.

Sidewalk's concessions "shows that Waterfront Toronto was able to stand up to Big Tech — not kick them out but not be bullied by them either," said Alex Ryan, SVP of partnerships at MaRS Discovery District, an innovation hub in Toronto. "People don't want it to be just Big Tech doing this development."

What's happening: Projects in other cities have hit snags.

Kansas City, Mo., is scrapping a city office responsible for managing civic technologies in favor of a 12-person board to advise on future projects, per StateScoop.

A watchdog group sued San Diego for not disclosing data collected by sensors and cameras via its controversial Smart Street Lights Program, per the San Diego Union-Tribune.

The big picture: Growth of smart city developments has been slower than predicted, but plenty of data-intensive technologies have been deployed in cities around the world.

Camera-equipped drones are used by public safety to monitor traffic, crowded areas and severe weather or emergencies.

are used by public safety to monitor traffic, crowded areas and severe weather or emergencies. Social networking monitoring lets local officials track citizen sentiment via Facebook and Twitter feeds to keep tabs on chatter and complaints.

lets local officials track citizen sentiment via Facebook and Twitter feeds to keep tabs on chatter and complaints. Location beacons at airports, transit stations, malls or stadiums can connect to your phone to detect when you are nearby.

Cities have been aggressive at putting in safeguards against technologies like facial recognition, and some are trying to forge data-governance agreements with the companies operating there.

Many data collection points start out as discrete projects. But as the amount of data being collected and exchanged increases, so do concerns that it may be compromised.

Going forward, city governments must get smarter about sharing the insights from the data collected, not the data itself, said Daubert.

"Generally speaking, city officials are incredibly cognizant of data privacy and doing what they can to meet concerns of people, largely because of what they’ve seen in the private sector," said Brooks Rainwater, director of city solutions at the National League of Cities. "That puts people in a place where they are asking more questions as these new services come online."

The bottom line: "This is something that every city globally is going to be dealing with in the next 5 years," Ryan said.