Yoga What?

I have been loving all of the yoga pics I've been find on Pinterest. Here are some of my favs -
downdog
this looks fun
so pretty
But every once in a while, I'll see something like this -
um...
This is a no no. You do NOT turn your head in plow pose. Ever. no matter how advanced you think you are. DON'T. TURN. YOUR. HEAD. You can get seriously injured doing this. 
whoops
Your knee is the one place you avoid in Tree Pose. Foot on knee - no. NO foot on knee. Anywhere but the knee please. 
another example
yeah - no
This isn't really incorrect form but doesn't really remind me of Yoga even though that's what it was entitled. Yeah, there's a little thing called Brahmacharya that seems to be a little counter intuitive to this pose. 
Just some observations from a new teacher point of view. I may learn something different in a year that changes my mind about any of these so who knows. That's what's kind of neat about life and yoga, my perspective always seems to be changing.