Uber driver Dennis Coder, 75, has owned restaurants and bars, nightclubs and natural-products distributors. “Nothing really surprises me anymore about how you have to take care of your responsibilities,” he said.

So he’s unperturbed by San Francisco’s announcement last week that all Uber and Lyft drivers must register with the city for a business license, ponying up $91 a year because they are independent contractors.

“Do I like it?” he said. “Not necessarily, but it’s just the cost of doing business.”

On social media and in private conversations, other drivers were less sanguine, with a few saying they’d stop driving in the city. But overall, most, like Coder, were prepared to swallow a relatively minor fee. For many, the biggest question remains: How did the San Francisco treasurer’s office get names and home addresses for the 37,000 drivers it said it’s contacting?

The city isn’t saying, other than that it took “nearly two years of enforcement work, including multiple requests for information and subpoenas,” as it wrote in a press release. The office can issue its own subpoenas. It has legal authority to keep them private, and it won’t disclose whom it targeted. Drivers who receive the letter can says it doesn’t apply to them if, for instance, they no longer drive for hire, or do so fewer than seven days a year in San Francisco.

Lyft said it had complied with the Treasurer’s request for tax data on all its drivers in 2014 and 2015, as it was legally obligated to do. (While Lyft only issues IRS 1099-K forms for drivers who make over $20,000 a year, that threshold did not apply in this case.) Uber declined to comment. In an email to drivers, Uber wrote, “We are also unsure as to how the treasurer's office obtained addresses for Uber drivers and we are looking into how that could have happened.” Some Uber drivers said they were certain the information came from the company, as they saw the same typos in their addresses on the treasurer’s letter as in communications from Uber.

“The fee is a pain point for drivers, but the bigger issue is having to publicly register as a ride-share business in San Francisco, said Christian Perea, who drives for both Uber and Lyft and writes for the blog The RideShare Guy. For instance, he said, drivers fear insurers could use the public database of drivers to snoop out those who haven’t informed their personal carriers of their commercial activities.

Lyft had a similar take, with concerns about stalking, for instance, since drivers must provide their “business address,” which for many is likely to be their home.

“To us it’s a big privacy concern,” said Lyft spokeswoman Chelsea Wilson. “We find it problematic that someone can go to a public database and look up a driver.”

Uber and Lyft both decried the requirement in emails to their drivers, saying it would hurt their flexibility and impose undue financial strains and red tape.

On the other hand, both companies have to walk a fine line, since by requiring the license, the city is concurring with Uber’s and Lyft’s view that drivers are independent contractors, not employees. Uber will go to court in June to battle a class-action lawsuit by California drivers seeking to be reclassified as employees. Lyft had tentatively settled a similar lawsuit, although a federal judge recently said the $12.25 million it offered to pay was too low.

In San Francisco, taxicab drivers must get business licenses, and some 6,100 have done so since 2011, said Amanda Fried, a spokeswoman for the treasurer’s office.

“We don’t intend to treat these (ride-hailing) businesses any differently than we’ve been treating all other businesses in San Francisco,” she said. “These requirements have been around for years and years. If you go into any restaurant, nail salon or other business in the city, you will see the business registration displayed.

“If there are privacy concerns for independent contractors, we‘re happy to figure out a way to make them feel secure in registration,” Fried said. “But psychologists and others with real privacy concerns hae figured out how to manage it.“

For all the brouhaha here, the requirement is common in other regions as well. San Jose, Los Angeles, Portland and the state of Nevada have business-license requirements for ride-hailing drivers, according to a website Uber maintains for new drivers about getting started in various locales.

“I’ve seen that other cities do it, so it wasn’t that much of a surprise,” Perea said. “My guess is that most drivers will ignore the letters until they start getting ticketed for not displaying the license.”

San Francisco business certificates, about the size of a folded piece of letterhead, are color-coded by year. This year’s color: hot pink. It should coordinate well with Lyft’s similarly hued glowstaches, if not Uber’s recently redesigned logo.

Carolyn Said is a San Francisco Chronicle staff writer. Email: csaid@sfchronicle.com Twitter: @csaid