I don't think MIT is freeloading from an ILL perspective-- The @internetarchive does ILL exchanges with 400+ libraries including MIT. And while MIT has gotten lots from us over the years, it is not in the top 25 libraries requesting.
So I suspect they use ILL and document delivery services (big $/paper) it is just they don't requests that many papers.
But that is not good news, really, we need researchers learning from each other.
We need OPEN!