Well, not really the chord progressions themselves (or maybe I am), but rather, how do you lump a whole song into one chord progression? For example, when someone says that a song is a I-V-vi chord progression, that implies to me that the entire song is composed of only three chords; the first, fifth, and minor sixth, and are played in that order. But when I look at the the actual chord progression of the song, there's a whole lot more than three chords, and there's more than one chord progression present. The verse may be I-V-vi, but then the chorus may be something different. If you have a song that's composed of eight chords and three different chord progressions (for verse, chorus, bridge), then how can you classify the entire song as being one chord progression consisting of three chords?