So there's this place in my mind where the notion is flawless and seamless and never abused but that's ludicrous. One of the things that could happen with the ability to upload data onto your identity chain is storage of information that was never yours to begin with. It would be the ultimate way to own copies of your (hopefully legally obtained) media files. Imagine having online access to your entire media library and having that data be utilized by applications to help you find more content you like or applications that utilize your media collection to guess things about your personality or determine where you are on a demographic scale. The iterations would never be copied, only pointed to. But they would never be deleted. Your identity blockchain would be this permanent indestructible record of everything you've ever uploaded and ways you've utilized each iteration of your own data across endless applications.
This could be a terrible thing if anyone ever accessed your password or managed to steal your encrypted identity. It could be a nightmare because they could put terrible things onto your blockchain that could never be undone.