I mentioned that an ISP can censor an ip address in their range. It sounds like black-hole-ing is a form of that. Thankfully, at least right now, it's easy to get around such censorship by renting a different ip address, since there are many ip address providers who do not require identity info. But I imagine it is difficult in some countries to rent an ip address without KYC, and if it becomes difficult worldwide, that will suck pretty badly.