I think "power sources," like "roles" and other 4e-isms, have been there all along but just were named for the first time in 4e.
And since it's in 4e it's wrongbadawful to certain people, even though the distinction has been in D&D from the start.
I disagree with the need for an "Item" power. If a Wizard made the item, it's Arcane, if a Cleric made it it's Divine, if a Psion made it it's Psionic or Mental or whatever.
Artificers or similar focussed classes seem generally arcane, so there's no need to have a separate power source for one class that appeared in a single campaign setting.
Really? I thought it had its origin in the witch hunts, the D&D analogue of which would have been Divine vs Arcane.The arcane/divine split, while a fairly artificial creation of E.G.G., is by now as sacred a cow as hitpoints.
4e then did this kind of weird thing where since there were 4 roles every power source needed at least 4 classes, and then started splitting out power sources so nature gods got split out as primal, etc.
I presume this last bit is what they mean when they say powersources are dead.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.