Although I didn't make much of it at the time (I don't know if anyone did), the CD probably symbolized better than anything else the popular shift into a digital age. I relate to the CD more as a music medium than a digital storage format, in the sense that my first relation to CDs was as a replacement for vinyl or tape albums. It's because of the impact that CDs had (or perhaps merely represent) on the reception of a formerly analog, social activity like music that as an artifact it symbolizes the analog to digital shift so well.
Inherent to the size and packaging of music CDs was the reduction in printed material in comparison to that of vinyl records. This drastically changed the nature of what an album was by diminishing the literal and graphic associations connected with any given release. There was about a decade of limbo between CDs as a popular music format in the late 1980s, to the mass popularity of the Internet in the late 1990s, when anything you wanted to know about a CD's contents was limited to the material printed on its liner notes (and in rare cases included in files on the CD).
All this influences how we perceive music socially, i.e. how we talk about music. The packaging to a vinyl record was a poster, a flag, for the army of a rock band's fans. A CD limits the army to those with 20/20 vision willing to squint to see a visual message, and to be honest, a CD is awkward and embarrassing to both have autographed or autograph.
So the CD doesn't just represent a shift from an analog to digital medium. It also represents a shift in emphasis in the literal and visual associations with a music artificact, and also a context for comparing a social activity's worth (e.g. as a medium, a CD might contain music, a video, an encyclopedia, or a game). Perhaps the more notable change though is towards how something like music is perceived. Rather than a cohesive representation of what a musician or music group is all about, the CD expects that the listener will (if necessary) supplement their understanding through other means, e.g. visiting the band's website. This is a fragmentation of the social, listening experience not only in the diversity in attention anticipated in the listener, but moreover in the popular reception of music as an individual experience (i.e. downloading to your iPod) as oppose to a group socialization (i.e. attending a concert).