IME, especially building APIs for mobile apps: nulls suck anyway!
Yeah, but nonetheless, are sometimes necessary. The suggested way is to just remove the field entirely, which is really a different sort of null.
Also, generic mapping types are second class citizens, id est just wanting to specify string -> string
I appreciate your point of view, but mine is different. For example, at Trulia, with a dozen different apps with millions of users and rich data in the app, there is a "no nulls" policy. It's just a convention: build sparse data structures instead of passing nulls.