I know it's been a while since someone has posted on this one, but besides all the very apt points already listed, there is one major one I think has been overlooked: PAGETURNS. A lot of composers forget this very important bit, especially (for example) when a string section carries on through six or seven pages without respite. Unless the composer intended those crucial sections to die down since half the players need to frantically switch to the next section while the other half try desperately to remember what is on the next page.
String sections have the biggest culprits, methinks, mostly because there are more stand partners and most people use them as the main focus for melodies and structure.... (And yes, I'm guilty of it too)