[jj12345]

These are good questions, but I'd also be curious to hear of some more concrete examples. In the interest of continuing the discussion, OP might be referring to some hybrid approaches like Backbone/Knockout where they aren't trying to solve some of the more interesting problems (e.g. bundling, dependency management, etc.). Of course, this ignores those problems and you could argue that different SPAs could be reduced to different "controllers" or some other framework specific abstraction.