Take the Kalmus editions of music, for example. Back in 2006, i purchased such an edition of the Visiions fugitive (Fugitive Visions), Op. 22 for piano by Russian composer, Sergei Prokofiev (1891-1953). I will say that, if Prokofiev were alive today, he would be furious (which was in his nature, anyway). Why? Because the Kalmus edition of this work is filled with editorial problems: many of which are painfully obvious.
Here's what's wrong with this version:
1) The title is incorrect. The Kalmus edition labels this work simply as Sketches, Op,22
2)This version claims to be an "Urtext Edition." This means that the score, theoretically, stays true to Prokofiev's original musical indications,
3) No publication and copyright information on the Title page-- There is no way of knowing when or where this edition was published.
4) No musical fingering indications-- While composers usually do not include this, some other musical editions of the similar pieces (e.g., the Alfred editions. provide suggestions for pianists on how to perform the music by indicating in numbers which finger hits which note.
5) No footnotes-- There is no evidence in the Kalmus edition that supports why Prokofiev wrote the music the way he did.
6) No English translation-- The majority of this score is in Italian and Russian: the latter of which do not speak or read fluently. Case and point, unless you are a polyglot (you can understand multiple langues), it is easy to get lost in translation.
These are just some of the problems that I found before throwing a fit. Yet, in all seriousness, musician have to consider all of these factors and more when choosing a good, thorough musical edition. Understanding this can make all the difference in the musical world.