One evening in New York City in early July, a frequent Uber passenger pulled out her smartphone and e-hailed a car through her Uber app. She was notified a car was on the way. Minutes later, the app told her the car actually wasn't going to pick her up -- but not to worry -- Uber was searching for another nearby driver.

Then it happened again.

"I was confused, because it wasn't that busy of a time," she said. "It was infuriating because my boss was with me and we were late."

A couple days later, the passenger (who asked not to be identified) ordered an Uber car again. Making small talk, she asked the driver about the canceled cars.

"He told me, 'You are only a 4.3. Your rating is really low,'" she said.

She had no clue what he was talking about. The driver explained that just as passengers rate their drivers, drivers do the same for riders. The only difference is that rider scores are anonymous to users. The rating system is 1 to 5, with 1 being the worst and 5 being the best.

"He said most drivers don't pick up people with scores under 4.7," she said. "He said he's not quite so stringent, so he will take people who have above 4.0."

Why have passenger ratings?

Uber isn't the only ride-sharing service that has passenger ratings. Both Lyft and Sidecar also have rider scores. Sidecar, however, is the only service that lets users freely see their ratings.

"Riders are able to see their overall rating on their Sidecar account," a Sidecar spokesperson told CNET.

The idea of passenger ratings is to help drivers share information about passengers and make the service as safe and respectful as possible.

"An Uber trip should be a good experience for drivers too -- drivers shouldn't have to deal with aggressive, violent, or disrespectful riders," Uber spokesman Nairi Hourdajian wrote in a blog post in April. "If a rider exhibits disrespectful, threatening, or unsafe behavior, they, too, may no longer be able to use the service."

Uber drivers have horror stories of door slammers, rude passengers and ride cancelers. And it can get even worse from there with messy eaters, vomiters, beer drinkers and drug takers. A handful of Reddit driver forums are full of such tales.

"I once had a young gentleman, business type, that I picked up from a hotel going to the airport," wrote Reddit user HectorMagnificente. "I had noticed that he was writing in a notebook with a very fancy looking pen. As I looked over my shoulder to check a blind spot, I noticed that he was stabbing his pen into my upholstery. I immediately asked him to stop and reminded him that this was my personal vehicle. He just sighed and rolled his eyes."

This incident appeared to be a one-off, however. By far, the biggest complaint among Uber drivers is passengers who make them wait unnecessarily or aren't in the exact location where they said they'd be.

Judging by the Reddit driver forum, many drivers are generous and give most people a 5. But other drivers are easily peeved and will give lower scores for small things -- if, say, passengers "smell strongly of body odor, foot odor, or even perfume or cologne" or do anything to "annoy me in some way."

The frequent Uber passenger claimed she never threw up in a car or canceled a ride at the last minute. So why was her rating so low?

"I'm really not very chatty, which might come across as rude," she guessed. Also, "I get impatient when they don't know where they're going. I can get snappy, but only a little bit snappy."

How can you find out your rider score?

The fact that Uber rider scores are secret makes them all the more intriguing. A simple Google search of "Uber passenger rating" brings up tens of thousands of results.

A couple months ago, a 19-year-old techie named Aaron Landy realized he could take advantage of a security flaw in Uber's website. He hacked into the system and figured out a way that everyday people could get their rider scores. He wrote up his findings, published them on a Medium blog and posted it to Reddit, Facebook and Hacker News.

"Right when I released the hack, I had a few friends who uploaded it," Landy said. "I went to dinner and I looked down at my phone and I had 200 Twitter notifications. It was pretty explosive growth."

It took only a handful of hours for Uber to fix the hole in its system. Landy then found another workaround, republished it, and again Uber shut it down. Landy says he wasn't the first person to discover the flaw, but rather just the first to make it public.

Uber has said it's not against making rider scores public, it just hasn't gotten around to doing so yet.

"We're exploring ways to show the rider's rating in the next generation of the app, but in the meantime, a user's rating can be obtained by simply asking the driver or contacting support," Hourdajian wrote in the April blog post.

However, Uber has updated its app at least once since Hourdajian's announcement and there's yet to be a simple way for passengers to get their score. The company did not respond to requests for comment about when this feature may roll out.

Lyft doesn't have any immediate plans to make its passenger ratings public; instead it believes an anonymous system leads to a more honest system.

"Safety is our top priority," a Lyft spokesperson told CNET, "and keeping this rating system anonymous ensures that ratings are given honestly based solely on the two parties' experience during the ride."

Should passenger ratings be secret?

Ever since the frequent Uber passenger found out she had an abysmal 4.3, she's been looking for ways to raise her score -- by being more chatty and trying to be timely during pickups. During one recent Uber ride, a driver told her that if she gave him a driver score of 5, he'd give her a rider score of 5.

"Now, I do that all the time," she said. "It's like a barter system."

While keeping passenger scores secret could lead to a more honest assessment of a ride, some argue that transparency could steer people to better backseat behavior. If passengers are aware they may get dropped rides, they might make more of an effort to be courteous.

"If it's not secret, it might make people behave better," the frequent Uber passenger said. "It's like getting a report card. You'll probably be a better Uber rider."

Updated at 11:25pm PT to clarify the Uber driver offered the frequent passenger a score of 5 if she also gave him a score of 5. No money was involved.