A hobby is something you do sometimes an addiction is something you do far more often than a hobby and can consume a large part of your life if you let it

Addiction is something you want to get rid of.

so alcoholics who don't want to get sober aren't addicted then?

What do you show to people around you if you do mountain biking as a hobby?

If you say photos you could also show photos of you and your frens consuming crack to other people. If you say the mountainbike itself, you could also show you collection of crackpipes to others.

this but unironically

you can't just say that and not show proof

Yes, if they genuinely don't want to quit it's just a hobby for them. There's a lot of dangerous hobbies out there - some people do BASE wingsuiting, some do alcoholic binges.

OK to elaborate further:

 

Over the course of last couple days I've written 28 pages (yes) of autistic ramblings (in fucking \LaTex, even).

This is clearly an obsession.

But if I actually manage to turn it into a serious book it will have been a hobby.

What are you writing about?

Definitions from Wikipedia:

1) A hobby is considered to be a regular activity that is done for enjoyment, typically during one's leisure time.

2) Addiction is generally a neuropsychological symptom defining pervasive and intense urge to engage in maladaptive behaviors providing immediate sensory rewards (e.g. consuming drugs, excessively gambling), despite their harmful consequences.

 

Key difference: Are there harmful consequences?

also leisure time

Well, you could argue that you think about your hobby during work hours sometimes, but that doesn't make it an addiction.

The probability to get lung cancer as a smoker is in the single digit range. The probability to break a bone as a serious mountain biker is probably similar or higher. Does this make mountain biking an addiction?

90% of all lung cancer deaths are caused by smoking and it more than doubles your chances to get coronary heart disease or a stroke.

 

And this is just a few ways it might kill you. It is bad for your health and appearance even if you don't die from smoking. You get more wrinkles in your face and your tits get saggier if you're a woman.

Your statement does not make broken bones less harmful.

Wrong! It's asbestos constructionings