"I don't like a system where anyone can make an artistic production unavailable to listeners or readers. In some cases this can be against the wishes of the person who created it in the first place, as with Celtic Records."

Many if not most contracts concerning written material (novels, screenplays, etc) nowadays have clauses stipulating that rights revert to the author should the publisher not release the work within a specified time period. I think this is a good thing and should become common practice in the music industry as well.
Unfortunately those under existing contracts without such a clause have no legal recourse that I can think of. The owner is within legal rights to sit on or even destroy the material.
Maybe enough public pressure could be brought to bear, a la ASCAP vs the Girl Scouts? Then again, we're just not big and public enough.
-Glenn