I think there is a place for productive criticism, and asking questions like "Why is it so hard to scale 4chan?" or "Why couldn't Amazon keep their cloud service online?"

But the key is you must be asking the question to learn, not just to ridicule. The intent can't be just to say "I could do a better job if I was doing it" but to discuss what shortcomings are there or improvements could be made with the goal of learning.