The fact that a sample question is too broad or too subjective is a terrible, terrible, terrible reason to vote the question as a "great off-topic example."
While there's a few proposals where people are voting as Robert says we should - the Theoretical Physics proposal comes to mind - those proposals do not make up the majority. Often, users will vote as off-topic a question that is subjective or argumentative which isn't the intended behavior.
What I propose is to change "not a good example" to "subjective or argumentative" or, if there's enough room for it, "subjective, argumentative, or duplicate."
That's a much clearer categorization and it covers most questions that are meant to be voted "not a good example." Additionally, by using the exact same terms, the voting process on Area51 will more often be reminiscent of the vote-to-close process to users with prior experience with Stack Exchange.
Moreover, having "subjective" a a clear "bad example" category should send the message that this is for objective questions only which can't hurt.
I also propose to change the descriptions of "off-topic" and "not a good example" to:
- Great off-topic example: This is a great example of a question that could be easily or commonly mistaken to be on-topic. (Click again to undo.)
- Subjective or argumentative: This question is subjective, argumentative, not a real question, or is too similar to an existing question. (Click again to undo.)
The current descriptions are unclear and don't really tell you what the two categories are for.