I would worry about the liability implications of such an approach. If one of those peers is storing (say) child porn, and some of that porn ends up on my hardware via automatic duplication, does that implicate me legally in their crime? If it does, does it matter whether it's on my hardware with or without my knowledge? If the police identify my hardware as part of that peer's storage network, is that hardware at risk of being searched and/or seized? That sort of thing.
