I was just thinking how different levels of prescriptiveness, different models of correctness are implemented on different genres or text types. Why for instance is the clipped language of newspaper headlines not considered ‘wrong’ while such usage would be criticised in many other types of texts? And a little closer to home: what is and is not grammatically acceptable in a blog?

If we distinguish between different genres in deciding what is and what is not grammatical or acceptable, does this then mean that specific prescriptive rules are nothing more than one aspect of a specific genre or text type?