Are yes or no questions useful on Stack Overflow?
Not all yes/no questions are easy to answer.
One such example of a non-closed Yes-No constructive question: Should this work?
The OP is asking if it should work -- Yes or No,
but yet the answer turns in a completely different direction.
A second example of a closed constructive question: http://stackoverflow.com/q/9056156/561731
The OP was curious as to why the browser showed no output, and the answer clearly explained why.
That one should not have been closed, because it seemed very constructive based on the answers given.
Wow this one is a yes no question, but under the flag of meta discussion