NEW YORK (MainStreet) — If you haven't tried Uber yet, it's clear that the mobile app ride-sharing service is looking to come to a city near you, if it hasn't already - and in the process making traditional taxi service irrelevant.

Instead of hailing a cab, registered users simply use Uber's mobile app - via their Apple (AAPL) iPhones, Android devices or Windows phones - to request a pickup location. Since registered users already have their credit card information saved in Uber's app, there's no need for cash and receipts are emailed. Uber has several ride-sharing options: a low-cost option, uberX, luxury sedans and seating for groups under UberBLACK and UberSUV as well as uberTAXI, which connects users to a taxi at metered rates. Uber drivers retain 80% of the fare earned, with the company taking the other 20%.

Founded just five years ago, the San Francisco-based company is already in 205 cities in 45 countries, with the company expanding into 24 markets just last week. The company says it has millions of users, but would not provide an exact number to TheStreet. However, Uber is up against strong resistance from taxi drivers in various cities across the world who have been in an uproar at the disruptive company, mainly for not being beholden to stringent regulations that other taxi drivers are required to follow. A number of cities, from Seattle to London have held protests against the company.

On Tuesday, following a lawsuit that was filed by Taxi Deutschland, a German court in Frankfurt temporarily banned two of Uber's three services in the country -- Uber and UberPOP, its ridesharing option in Europe. Unlike UberBlack, the first two services do not require the use of registered drivers, according to Fortune.

"Uber will carefully review the content of the preliminary decision of the Frankfurt Regional Court, and will appeal this decision and vigorously defend the claim that has been filed by Taxi Deutschland," Uber responded in a blog post on Tuesday. In the meantime, "Uber will continue its operations - and will continue to offer its services via its app - throughout Germany."

Last week Illinois Governor Pat Quinn vetoed legislation, House Bill 4075, dubbed the "Uber bill" and a related measure under House Bill 5331 that would have imposed statewide regulations on commercial ridesharing and preventing local governments from adopting rules to fit their communities. "I am vetoing this legislation because it would have mandated a one-size-fits-all approach to a service that is best regulated at the local level," Gov. Quinn said in an Aug. 25 statement.

Uber, which raised $1.2 billion in June at a pre-money valuation of $17 billion, is also experimenting with other delivery services like messenger services through UberRUSH in New York City, a ridesharing option, UberPool, that's in beta testing in San Francisco; the Uber Corner Store launched in Washington D.C. last month, and, from Aug. 26 through Sept. 5, it is experimenting with UberFresh delivery service in Santa Monica, Calif. Investors in Uber include Goldman Sachs (GS) and Google (GOOGL) , through Google Ventures.

The company sees itself as a technology company not a transportation company. "We assess a number of factors before entering a market, including existing regulations and user demand. If the laws haven't conceived of Uber's model, we'll reach out to policymakers about the significant demand in their city and educate them on this new paradigm," Uber spokeswoman Natalia Montalvo wrote in an email to TheStreet on Tuesday.

Here's five U.S. cities making it harder for Uber to do business.

Little Rock, Ark.

Uber is trying to get off the ground in Little Rock, but it is currently prohibited there. The city is gearing up for a debate on the ride-sharing service, with varying positions by Little Rock's board of directors on whether to allow the service in the city, according to the Arkansas Times.

Uber has apparently "suggested revisions" to the city's code to allow it to operate, the Aug. 20 article said. A follow up article by the Arkansas Times sheds light on a fact sheet that Uber submitted to the city in hopes of persuading Little Rock.

"We're in the really early stages of the process with them," said Luis Gonzalez, communications and market manager for the City of Little Rock, who confirmed to TheStreet that currently the service is not allowed there.

Uber representatives are tentatively scheduled to meet with Little Rock's board of directors this month to take a closer look at the city's transportation ordinance to see what, if any, revisions would be needed to accommodate Uber. "That's going to be the first step," Gonzalez noted.

Las Vegas

The glittering city of Las Vegas is still without an Uber outlet, while other smaller cities Uber away. According to Uber's Twitter feed, @Uber_Vegas, the state's outdated regulations are the cause of the absence.

@shanereiser, wish we could bring safe stylish rides to LV but state won't allow. Hope lawmakers give voters what they want #VegasNeedsUber

— Uber Vegas (@Uber_Vegas) March 17, 2014

Nevada's taxi and limousine regulations are among the strictest in the nation, according to the Las Vegas Sun.

Portland, Ore.

Uber has also set its sights on Portland, Ore., but so far, the city's makes it illegal for Uber to operate there. Portland has started to look at ways to modernize its tax regulations for the sharing economy, according to a July 30 article from The Oregonian.

Portland Bureau of Transportation, which took over responsibility for rideshare regulations on July 1, does not currently have a timeframe for the amended regulations.

Richmond, Va.

Following a June cease-and-desist order by the state of Virginia to Uber and its competitor Lyft, last month Uber and the Commonwealth state cleared up its differences so that the company could have temporary authority to operate in the state.

Uber announced on its blog on August 6 that it was uberX would be available in Richmond, Va.

Two more cities in Virginia - Charlottesville and Blacksburg - were added as part of last week's Uber launch in an additional 24 markets.

Cambridge, Mass.

While Uber isn't currently prohibited in Cambridge, the city is trying to figure out how to regulate it. Cambridge's board of License Commissioners held a public hearing on June 17 to discuss draft regulations for smartphone technology, which mainly includes concerns about public safety - driver background checks, regular vehicle inspections and adequate insurance.

The city stated in a press release that while it "has no intention of stifling innovation or removing transportation options," it does "have an obligation to ensure that transportation industries falling under their regulatory authority provide safe and accountable service to the public."

Final rules have not been completed yet. "We're still kind of looking at our next steps," Andrea Jackson, chairwoman of the Cambridge License Commission, told TheStreet on Tuesday, who added that there should be an update in the next month or two.

--Written by Laurie Kulikowski in New York.