I wish to add a legally robust "blockchain clause" to all of my projects' licenses that disallows use directly or indirectly in blockchain-related projects. If there are any that already exist, then Ideally I wouldn't need to hire a lawyer to draft one up, but I might be willing to pay if the costs aren't too high, knowing that others would then be able to use it freely.
I personally would want to see lots of widely-depended on open source projects adopt such a clause, whatever dangerous precedents that may come with it.