If we're borrowing some of the concepts from the more modern mythologies, there seems to be a rather pervasive idea that gods are in competition for the soul. Whether it's down to two primary entities vying for control, or multiple incarnations, that seems to be a fairly common thread.
In that respect, for game terms, I agree with Lord Miller as well. If souls are the currency for the spiritual stock market, then simply declaring them for one brand or another should lend value to the stock. I.e. worship, in and of itself, is enough to complete the act. One must assume that a being with that degree of power must have the ability to either convert declared soul "energy" to raw power, or that indeed, the deities play a game amongst themselves where the power to dispense magic to followers is weighted by one's current standing within the pantheon.
If, however, we are looking at a truly polytheistic setting, where gods are considered to be real, then common people will likely pay service to ALL the gods in one form or another, to avoid offending any of them. Then, we look to rituals, offerings, songs, prayers, and various sundry forms of worship in total, and there would seem to be a reasonable expectation that the energy derived from these offerings would be shared among the gods, otherwise competition for direct service would be more fierce.
So yeah, collectivism or capitalism, with worship or declaration of souls as the currency.
