Jack99
Adventurer
For example: I have NPCs who have received magic items from PCs, who undertook quests to retrieve said items for said NPCs. Such magic items have powers usable 1/day (think Teleport, or Heal - both extremely useful power from 1E - 3.5E). With 4E, the NPC can only use one magic item power with a 1/day power, even if he, she, or it, has 5 such items. According to the 4E rules (as I understand them), my 7th level NPC could only use one such power per day, in spite of having 5 magical devices each with a 1/day power. That is a good way of balancing magical items with the rest of the 4E mechanics. But a player whose character went on a quest to retrieve one of these items for that NPC is rightly going to question why should he have bothered. Then why would the NPC go to the trouble of gathering these (mostly) useless items for himself? Versimilitude, setting, and NPC/campaign motivation killed by a game mechanic. This is a fundamental balance issue for 4E - 1/day magical items can only be used a limited number of times, no matter how many 1/day items the character possesses.
Technically, this is not entirely correct, for what it is worth. As a basis, you may use a dailies once per day. However, with each milestone acquired (by the book a milestone is two encounters without an extended rest - an encounter could be a skill challenge as well) you gain the use of another daily item. So if your NPC goes through 4 encounters in a day, he would be able to use 3 different dailies. I know that quite a few people have experimented with players being able to use 1 daily per encounter, without reporting breaking the game.
What that is said, these rules apply to players. The general attitude in 4e is that NPC's should be able to do what the DM wants them to do, instead of being modelled as pseudo-PC's.
Cheers