Disclaimer: I don't claim to be an expert. The stuff in this email could be false. If you use it, use it at your own risk. Also, since about 7/05, I've earnestly tried to keep my large-scale internet presence politically/religiously neutral. Stepping on big toes with such new and powerful technology seems highly incautious in my case.
Application of disclaimer: I do not intend to comment on the ethicality of manipulation versus persuasion for other people or organizations. I only intend to give my own standard.
Two words sum this up for me: Informed Consent.
I don't want to unnecessarily and deeply persuade someone without their informed consent any more than I would want to have sex with them without their informed consent. Either way, I imagine that I would feel like a rapist.
But, that is just me, and I don't intend to try to persuade or convince others of this viewpoint.
Informed consent.