Interesting; for me line seems fairly thick at "ownership" level (which just shows we may have different assumptions:)
My thoughts:
If it's in my inbox (whether on my physical phone, or hosted for me by a service provider), I own it and I get to control it regardless who sent it / how it got there (as long as other legal pre-requisites are met, i.e. not child porn etc)
If it's in my outbox, and I want to delete my account, THOSE instances of those artifacts should be removed, whether from my physical phone or by the service provider hosting them for me. If I've sent them to others, fair game, they own THOSE instances; but I expect the service provider to remove, upon my request, the artifact instances I solely own.
My thoughts:
If it's in my inbox (whether on my physical phone, or hosted for me by a service provider), I own it and I get to control it regardless who sent it / how it got there (as long as other legal pre-requisites are met, i.e. not child porn etc)
If it's in my outbox, and I want to delete my account, THOSE instances of those artifacts should be removed, whether from my physical phone or by the service provider hosting them for me. If I've sent them to others, fair game, they own THOSE instances; but I expect the service provider to remove, upon my request, the artifact instances I solely own.