Suppose I post a question whose body consists of a link to a math.SE question and then I proceed to ask "I want to know what economists think about this?"
Is this crossposting? Technically most of the information is located in one place, the math.SE question, but then what is the point of my post here? Should it even be answered here? Wouldn't that result in the same inefficiences as crossposting?
Does it make it worse if I put a bounty on my advertising question?