It's a great idea, but I'd say forbid probably is a strong word. =) Sometimes (and I include myself on that list), users face questions that should be built from the ground, starting from a basic code which is relevant to the context. As an example, one of my questions started with "Consider the following code" mainly because I couldn't simply tell what I'd like to achieve before providing some background. The question description, when listed in the front page, was not useful at all, but I managed to give it a good title, so the question was somehow saved. IMHO the problem raises when both title and body are not descriptive. If the title is good enough, I'd probably say to leave the question as it is. Besides, some non-native english speakers (like me) have difficulties on providing a good summary. =)
PS: I'd like to write this text as a comment, but it exceeded the maximum lenght for that.