Interesting, if somewhat dubious, research. The example given from the political speeches is inconclusive -- Obama is taking quite a different sort of opening tack from Washington. Perhaps it is broad rhetorical approaches that are changing; there's nothing inherently 'formal' about 'the', though it'd be informal to use a lot of ellipsis, which might include eliding the definite article. (For instance, if I'd started sentence two of his post 'Example give from political speeches...')
