It depends on how the question is asked.
If the question really is "Why do I get a NullReferenceException at model.Foo", then it's perfectly fine to close as a duplicate of the canonical "What is a NullReferenceException and how do I fix it?", because the phrasing alone shows that OP lacks basic debugging and searching skills.
See also "Null Pointer Exception" questions closed as duplicates.
Feel free to create a more specific canonical MVC Q&A about how the model binder works and how to properly generate a form that will be successfully bound, but until that exists, I'm fine with the closing you see.
And in the end, it always comes down to "You messed up your form generation code", so I think it'll be fairly easy to create a canonical Q&A about this.
You really don't want to spend your effort to explain every variation of these typos and misunderstandings, while as you say yourself, all those errors fall in like a handful of categories.
I'm also interested in this (I'm trying to be quite active in the asp.net-mvc tag as well, and I see multiple of these questions on a daily basis), so perhaps we can coordinate creating this Q&A.
