<p>just wanted to gather different ideas and perspectives as to which layer should (and why) LINQ fall into?</p>

I think LINQ should be the very lower-level (DAL) and I think it should be wrapped into a BLL.
I know a lot of people like to use the partial accessibility of the models that LINQ to SQL generates but I think you should have clear separation of interests (see what I did there?).  I think if you're going to have business logic it needs to be decoupled completely from your data access logic.
I think what makes it tricky is the fact that you can keep chaining those LINQ extension methods anywhere you have a using System.Linq line in your code.  Again though I think LINQ belongs with the definition and should be at the lowest possible level.  It also makes TDD/Unit Testing much, much easier when you wrap the usage of LINQ in a BLL.