I'd like to see what's in the download queues of the most recent RIAA case defendants. I strongly suspect that the large majority of songs downloaded are "Top 40", "hit radio", ClearChannel bubblegum pop. Whatever's most profitable right now. This certainly does not include established artists or "niche markets".
You might say "yeah, what else?" Exactly. If the above is true the RIAA, which was formed to protect the copyright of all artists, would only be concerned with what is most profitable for them at the time of subpoena. No one here will ever know if this hypothesis is true or not save being served their own RIAA court order. Still, it's not inconceivable that the RIAA could care little about those copyrights that aren't bringing them the lucre just now.
Should the above scenarios prove true, the RIAA would have betrayed its mission: the ostensible protection of all artists. Many people, including myself, strongly suspect that this is already the case. Nevertheless, we'll never know without knowing the specific songs downloaded and their immediate market value.
The RIAA's irrelevance does not extend merely to the massive shift towards online music purchasing/leasing. The very idea that a copyright protection agency could/would only prosecute those that violate the copyrights of the most "valuable artists" is a slap in the face to any recording artist.