Consider this - your character is hit by a crushing despair spell, a bane spell, and within the area of a L8+ Enchantment specialist wizard's Aura of Despair ability - you are at -5 to attack due to fear and sadness.
Consider the opposite - your character is affected by a good hope spell (counters crushing despair), a bless spell (counters bane), and a L8 Bard's Inspire courage ability (+2). You are at +2 to attack, because all three effects give morale bonuses.
In my opinion, all those negative abilities should be morale penalties, rather than untyped penalties. All the arguments for stacking bonuses (the sidebar on page 21 of the DMG) apply to stacking penalties as well (yes, the SRD should also have made bane and cruching despair morale penalties, not untyped penalties).
