Henry Fogel, the President and CEO of the League of American Orchestras and former President of the Chicago Symphony maintains in his blog, On the Record, that artistic interpretation of music by conductors and musicians has become narrower and more "puristic." He has proof of his assertion from recordings that have been made over many, many years. Fogel states that artists were much more daring and risk-taking in the years up to 1950, but since then artists have shown a narrower understanding of the right way to interpret music. You can read about Fogel's view here.
With more and more recordings and concerts turned out each year, it seems that we would be greeted with a wider variety of interpretations, but I wonder if we (artists, critics, and audiences) have straight-jacketed ourselves into thinking that there is only one right way to do a particular piece. I have a recording of Sibelius' 2nd Symphony that is directed by Toscanini, and it clips along at a faster and more furious rate than any recording by other conductors (all since 1960) that I have ever heard. I know that artists want to put their own stamp on how they do a certain piece, but perhaps many also fear that they will get clobbered it they express themselves too freely.