> a central database can be manipulated to effectively rewrite history That's true, and that's an important issue. But I might still ask, for each application,

> a central database can be manipulated to effectively rewrite history That's true, and that's an important issue. But I might still ask, for each application, is there someone who's trusted to introduce records into the system but not to update them later? (We can definitely envision applications where the answer might be "yes" -- often related to concerns about censorship -- but it doesn't seem like this is the case for every application.)