Is a past action still regarded as "dangerous" even if no one gets hurt?

Yes. Risk doesn’t say “something bad will definitely happen”, it says “the likelihood of something bad happening is increased by x amount”. Open heart surgery is risky, and all those open heart surgeries that resulted in exactly zero going wrong and the patient getting better doesn’t make it any less risky.

And car accidents can happen at low speeds on fairly unpopulated roads, and the whiplash even with a seatbelt can be quite painful and chronic. I say this from experience. Love your neck, it’s the only one you’ve got.

It’s reckless behaviour, and therefore can be classified as dangerous. Your second example not so much.
If someone let a firework off in an enclosed space full of people and no-one got hurt, would you retrospectively say that what he had done was not dangerous, creating a situation fraught with danger? Everyone was in danger, despite coming away safely. Everyone on the Titanic was in danger of dying that night, therefore they were in a dangerous situation caused by a cumulation of dangerous (i.e. risky, reckless) behaviour. Those that survived cannot be said to have not been in danger, upon reflection.

I would say yes, too. It was and is dangerous, regardless of the actual outcome. Of course, the degree to which something is dangerous depends not only on the likelihood of a bad outcome, but on the severity of said outcome. Not all dangerous actions are equally dangerous, in other words.

“Danger” is all about risk. It is not something where someone can predict, with any degree of certainty, what the outcome might be. Anytime you engage in ‘dangerous” or risky behavior and don’t end up killing or injuring yourself or someone else in the process doesn’t mean that what you did wasn’t dangerous or risky to begin with, it just means you beat the odds. Next time, you, or the person you run into, in a case like this, may not be so lucky. 

Yes! I did not even watch the video, but I am right now recovering from a bad accident where I was the passenger in a golf cart and the driver went speeding down a hill, and when I looked at her and her feet (because I was checking to see if she was braking) she said along the lines of, “I know it’s a little scary, but I’ve done it before it will be fine.” Seconds later she lost control, we swerved back and forth tipping up on two wheels, back and forth, and then finally slamming into a fence on my side. I was thrown into the fence. I have chainlink cuts on my stomach, cuts across my breasts, my entire right side badly hit and bruised, left a little two, road rash all over me, and I had a small tear in my left lung, and severe vertigo. My girlfriend who was on the back , has a 5 inch skull fracture, subdural hematoma, and concusion. I was in the hospital three days, my friend over two weeks, over a week was ICU.

The driver was an idiot to take that risk with us. We assume people will be prudent, cautious in their driving, and she took a terrible terrible risk. I would never ever take a risk like that, and I find it disgusting she put us in that situation. Just because she had done it before and nothing happened, did not make it any less risky. I am not a risk taker, never was, never will be.

Dangerous is dangerous and because you get away with it once or twice doesn’t make it less so. It is like playing Russian roulette. You won’t play it for very long.

It’s about probability.

Allowing the outcome of a decision to skew your perception of its true risk is a common cognitive bias:
Outcome bias

People driving at twice the legal / posted speed limit are a danger to others as well as to themselves. Other drivers may be incompetent or inattentive to a degree that won’t get them in trouble at normal times (including driver trainees, pedestrians, bicyclists, etc., who depend on “reasonable speed” by others) and find themselves involved in an accident by virtue of the excessive speed of your hypothetical driver.

EDIT: In addition, having now seen your video, it’s easy to “overdrive” the road you’re on. Overdriving is the condition where you travel faster than you could react “in case an obstacle came into view”. That is, if you can’t see something in the road ahead because it’s temporarily blocked from view by fog, darkness, a curve or grade of the road, and it comes into view only when you round the curve, your lights finally shine on it, etc., then you may not have time to react and stop or change direction safely to avoid it. “Don’t drive faster than you can see”, in other words. That driver was overdriving a lot of the curves in the road. Just because there was nothing but clear road beyond the curve doesn’t mean that each one wasn’t a huge risk – to himself and to whoever else could have been there. And that was by no means an unpopulated road, either.

By definition. dangerous means; Able or likely to cause injury or harm.
The final outcome doesn’t change the meaning of the word. He was fortunate.

We can assume Murphy’s law would apply here. SO true…..so true

I used to ride my bicycle with no helmet in traffic (they didn’t have helmets then), and I used to play at construction sites.

Even if I never got hurt, both of those activities were inherently dangerous.

The government will TELL you what’s dangerous and what’s not, if it wants you to know.

I agree- it is dangerous due to the potential for disaster.

A few years back a movie showed kids who would would lay in the road on the center line. Nobody was hurt in the movie, however kids were killed mimicking the stunt.

Stupid is as stupid does.

Also check out The Darwin Awards for a refresher on those who did not think what they were doing was dangerous.

@Dog Your answer reminded me Oprah’s campaign to stop driving while texting. So many people said they didn’t think it was dangerous. Huh? How can taking your eyes off the road not be dangerous? I still cannot understand how, what, uh, WTF people are thinking?! I get really pissed when TV shows show people driving (it’s fake of course) and the driver turns their head to the passenger as she talks. My parents would have forbid me from the car if they caught me doing that.

@JLeslie how funny. When I see someone doing that in a movie I holler “Watch the road IDIOT!”

It’s possible that you are getting confused by word tenses. You want to say that it can’t be dangerous anymore because it is already done and nothing bad happened. My response would be that what we know now is that no danger actually came to pass; but it still is the case now that it was a dangerous thing to do then. So the act was still dangerous, it’s just that none of the dangers materialized into harms—this time.