I think its criminal appeal is limited compared to alternatives. Use of a known and traceable payment+communications channel reveals more info about the perpetrators and their networks than non-crypto communication channels + crypto payments. Pairing communication and money removes a level of anonymity because of the traceable nature of blockchain transactions.
To make sure I understand, are you saying, "Every client developer has to handle this on their own, if they choose to at all"?
> I think its criminal appeal is limited compared to alternatives. […]
It seems like you're suggesting that anonymity is not possible with Ethereum, but searches suggests that it's possible now, and will become easier thanks to projects like Project Alchemy. (I don't know much about Ethereum, though, so I'd love to hear your thoughts!)
It kinda makes you wonder if the Ether wallet itself that can sync and download such data is also at risk of being called illegal.
Are FBI raids now going to focus on targeting people that have a copy of the block chain to put them away?
On a different note, Sone - microblogging over Freenet - has been around for quite a while, and it's under active development.