Those are "easily" manipulated if the issue is important enough to someone powerful enough. Sure, you could carpet-bomb and publish your hash on many different platforms under jurisdictions with competing interests, but at this point you've just invented a poor man's blockchains.

Blockchains are the systematization and democratization of that strategy. And those points are what technology is all about.

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Sure, to write our next shared article we can just have our Word files and call-up each other and exchange paragraphs over WhatsApp. Yet for some reason some people nerd out on unintuitive over-engineered CRDTs. That can't be useful to anyone, can it?

> Those are "easily" manipulated if the issue is important enough to someone powerful enough

Perhaps in theory, but in practice it's not really true, especially with regard to the nature of information that is worthwhile to censor; the kind of situation where the powers-that-be would hack twitter to manipulate the timestamp of a hash string are very far-fetched.

"Very difficult" is context dependent. It might be difficult for you and me to backdate a tweet, but easy for a Twitter employee or a hacker with a 0-day exploit.

You also introduce the risk of your message getting deleted, for whatever reason.

And these ways may also break your anonymity or leak your exploit if you're not careful.

A blockchain backed timestamp is simply better.