sniffles said:
I would say it is unreasonable for either effect to force the player to reveal info he really doesn't want to. Charm Person states that the target regards the caster as 'a trusted friend and ally'. If the PC would tell such information to a trusted friend, then it is reasonable for him to do so, but if he wouldn't tell that info to anyone if he could help it, then he shouldn't blurt it out to the caster of the spell.
I've seen some misinterpretation of Charm Person - the spell description states that it does not allow the caster to control the target as if he were an automaton, but many GMs and players in my experience seem to think the spell is equivalent to total mind control.
Just a point - from charm person
The spell does not enable you to control the charmed person as if it were an automaton, but it perceives your words and actions in the most favorable way. You can try to give the subject orders, but you must win an opposed Charisma check to convince it to do anything it wouldn’t ordinarily do. (Retries are not allowed.) An affected creature never obeys suicidal or obviously harmful orders, but it might be convinced that something very dangerous is worth doing. Any act by you or your apparent allies that threatens the charmed person breaks the spell. You must speak the person’s language to communicate your commands, or else be good at pantomiming.
Charm person is more powerful than just making the target your friend. I don't think it should be, but it is. Less powerful than dominate to be sure - but more than you give it credit for.
As for me - I apply the 'immune to dip/bluff/intimidate' on both sides. Bluff makes someone think that YOU believe something is true. Diplomacy makes someone (potentially) your best friend, not a mind controlled slave. Intimidate does the exact same thing (only replace 'best friend' with 'friend'). You're not going to be able to seduce the average character away from something important to them without a hell of a setup first (ie - you know he/she is single, interested and has someone to cover for them, or reasonably think they won't get caught/nothing will go wrong). You won't be able to intimidate the average henchman into giving up his boss, unless there's already some weakness there (the boss isn't particularly scary or benevolent, or again - you could set up ahead of time: evidence that the boss already dropped him in it, the head of his boss, that sort of thing).
Note - I'm not saying that you have to give a long, complex speech and I'll be swayed by your presentation, but in much the same way as making tactical choices in combat, out of combat interactions will be far more effective if you do more than just "charge him and hit him with my sword" so to speak.
In general - taking out a foe through social interaction should be as hard and varied as taking them out through combat - sometimes they're just waiting there for a friend (with combat: the creature is asleep, all your spells are targeted at his weaknesses etc), sometimes you have some work cut out for you (the foe is awake and alert and you have no special advantage), and sometimes it's just not gonna happen (the foe is awake, alert and happens to be immune to all of your primary offensive tactics). Other parallels (ie - the entire party should be involved, preparation makes a huge difference etc) can also be drawn in a manner that will greatly enrich the social game.