I've been training for almost 20 years (I'm also a Registered Nurse) and I'm still stressed when people get choked out.
My very first tournament as a white belt I put someone to sleep with an Ezekiel.
I wouldn't say I make a habit out of it, but yeah, I enjoyed it! :) 
Another RN/grappler here, and fuck that.
That's fucked up.
I agree, not a good idea.
Sure usually they will wake up just fine with no problem at all, but you ARE tempting fate anytime you put anyone unconscious, for any reason. If the reason is simply to show off or just for fun or something, that's not a good enough reason.
Correct as usual Mr Shen
No thanks. Who's the guy in the video?
Dion Watts. Wattsmma.com
No bueno.
No good
Usually it´s not dangerous but there articles from people who got a stroke or something. I think if some plaque from the arteris is going loose it can cause serious injuries. So I wouldn´t do it for fun.....
There was a doctor on here before who had some interesting comments, but I don't want to speak on his behalf.
There are zero consequences and short/long term effects to being chocked out. 
Yeah I used to think it was really cool/funny to do when I was 17. By the time you are a grown man (especially in an instructor position like that video) that is ridiculously inappropriate. Like others have said 99.99% of the time it'd harmless, but why tempt fate?
Good bye brain cells....
knee smash - There are zero consequences and short/long term effects to being chocked out.
The odds of all sorts things happening (e.g. stroke) are much higher immediately after you have been choked unconscious --or in fact gone unconscious by any means.
You also lose a lot of brain cells, not a ton, about as many as if you had an alcoholic drink.
If somone isn't 100% healthy/normal and has some underlying vascular issus --even one they arent aware of-- you could create a real problem by strangling them unconscious. I've never heard of anyone lapsing into a coma, having a stroke or seizure or dying from positional asphyxia after being armbared, but those things have happened when people have been strangled unconscious.
So to say there are "zero consequences" is just not correct.
Shen do you have sources for those claims?
Well, we had a forum member here (Bittencourt) who had a stroke from being strangled. Here's another story of it happening to somone else...
Story of a stroke from being choked:
http://espn.go.com/mma/story/_/id/8660482/sean-entin-life-choke
Death from Positional asphyxia after being strangled (one of the main reason cops don't use the ol' sleeper hold anymore):
https://www.ncjrs.gov/pdffiles/posasph.pdf
Effects of frequent strangulation:
http://www.pottstown.org/DocumentCenter/View/211
Dangers of people using frequent strangulation in BDSM context (I know, I know):
http://www.jaywiseman.com/SEX_BDSM_Breath_Medical_Realities.php
As I said above , it's NOT dangerous most of the time to most people, BUT those who have health issues, it certainly can be. Even if you are simply over 40, the risk of causing an arterial plaque to break free is more likely --not super likely-- but much more of a possibility. You're dealing with fundamental processes of the human body when you strangle someone, of course things can go wrong.