Power sources. What's the point?

[doctorhook]

Power source has some mechanical effects; for example, the wizard's spellbook. Wizards can learn additional daily and utility spells beyond what they can use in a day, thanks to their spellbook class feature. As I understand it, if a Wizard multiclasses as another Arcane class, (ie: Warlock), the Wizard can use his daily and utility Warlock spells in conjunction with his spellbook class feature. In contrast, he couldn't use his spellbook with any daily or utility exploits or prayers he'd have learned from multiclassing into a Divine or Martial class.

I'm sure there are other examples, and that there will be more in future products, but this was the first example I thought of. Certainly, power sources have at least a little mechanical basis.

I think you got it wrong. You can only add spells that you have access to, and rituals.

...

From my rereading of the text, I can't see why a Wizard/Pact Initiate couldn't add his Warlock spells to his spellbook. Since multiclass powers generally replace one of your primary-class powers, and since Warlock powers are known as "spells", I can't see why a Wizard who has multiclassed as a Warlock couldn't include his Warlock daily and utility spells as a part of his selection of daily and utility spells to choose from at the start of each day. In essence, as a multiclassed character, he does "have access to" whichever Warlock powers he has selected, hasn't he?

(As to whether or not such a character would be allowed to choose to add to his spellbook two Warlock spells -- or a Warlock spell and a Wizard spell -- I have no idea. I'd love for an informed, neutral third party to come and set me straight, but I consider that to be beyond the specific scope of this debate.)