Practical and legal concerns make such an operation a necessity. Of course it's not guaranteed to work, it relies on trust, but you can't make a system intended

Practical and legal concerns make such an operation a necessity. Of course it's not guaranteed to work, it relies on trust, but you can't make a system intended for real-world use where you can't at least attempt to delete things. Additionally, though the technology can't force other instances to delete things, other concerns perhaps can. Consider the potential legal implications of deliberately ignoring delete requests.