Have you ever been around someone who is blacked out from drinking alcohol? If so, did they behave in a way that is

Yes, however I was not aware they were in a blackout at the time. 

It's likely that I have been, but I don't know for sure of any specific time it's happened. I can remember my best friend telling me he didn't remember certain things from a drunken night, so I can assume he did black out at some point, but I wouldn't have known when. 

  To my knowledge, I have never been in that situation. 
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When I managed an enlisted man's club in the Navy, a sailor was so drunk he passed out and we didn't know until closing time. I had to call the hospital. I know a woman that was so drunk she had no recollection of the night before.

Yes and yes. People don't generally act like themselves when they're in a drunken stupor. I've been around many drunks in my life.

not yet

If you are blacked out you don't behave in any way.

Early one morning I awoke to a weird thumping sound outside. A drunk just drove her car through the bushes in my front yard. It is on a hillside so the car was having trouble escaping. She almost hit my house so I ran outside in my pajamas and yelled at her. I got an I.D. on the license plate and called the cops. She escaped after tearing up the front lawn. The cops caught up with her and the boyfriend came and gave me some money to fix the lawn. I guess the judge liked that. She remembered nothing of the incident.

Blackout doesn't mean they don't know what's happening in the moment, only that they don't form memories of what's happening. It stands to reason that someone who is that drunk isn't going to be super aware of their surroundings, but that isn't what the term references. Therein lies the conundrum- we have no way of knowing whether someone was blackout drunk until the next day or later, and that's only if they are willing to admit they were wasted and/or don't remember any of it. As the bystander in the moment, we wouldn't know- we can only tell they're wasted. 

If you get that wasted, you have a problem. Most won't admit it, but any form of binge drinking signifies a problem. It doesn't have to be a regular occurrence or every day thing. I have been around both types- those who depend on booze every day and those who drink to excess when they do drink. 

In my experience, they just act drunk and stupid. Not necessarily out of character, but their worst traits come out in full force. i.e. The belligerent types will just become angrier and meaner. The jovial types will want to keep the party going even when they can't stand up anymore. The ones that are hungry for affection will grab any available partner. 

Virtually any amount of alcohol impairs your judgement. Drinking and driving has little to do with blackouts and more to do with the fact that people aren't good judges of their own level of inebriation. Once you're intoxicated to the point your judgment is off, you could drive and not realize you're drunk. Depending on your size, you could be legally drunk after one drink. By 2-3 drinks, most people are impaired. Well, a beer or a shot is one drink, so if you're having a cocktail or something, odds are, you're legally impaired after one; man or woman, regardless of size. This is why it's really important to plan your ride home before you go out. You have to have a designated driver or be using Lyft/ Uber from the start because once you've got a drink or two in you, you can no longer trust yourself to make the right call.

I know some people will read this and think "I'm fine after 4-5 drinks." A few people might be, but chances are, you're not as fine as you think you are. There are some apps on the market that let you test your reaction times. Try it while sober and then try it while you're drinking. 

I'm the adult child of alcoholics. My mom had a stroke and now has vascular dementia and no use of her left side because of her drinking. My best friend in junior high/ high school was an alcoholic. She made several poor decisions as a result. She had a promising military career ahead of her. She got chlamydia in high school and became sterile. She got a DUI at 18 and then later struck another vehicle while driving drunk. She fled the scene and wound up in prison by age 19 or so. I have another family member who has lost everything to booze and an ex who has done largely the same and has already had a heart attack in his 40s. When you're in the thick of it, you don't realize how bad it is.