[qqii]

As long as twitter can act as a trusted third party, tweets are a completely valid ledger as shown by Keybase.

Blockchains simply reduce the power and trust required in the third party by offering a different set of tradeoffs.

[stagas]

You don't really need Twitter, you need a platform and require the people that use the platform to bring in their ledgers so they are auditable by the public. I can view someone's work and examine if they're trustworthy or not. Similar to how people are signing their signatures, they could be just bringing together their ledger, which could be a bloom filter so it's just a single line of hash that I can verify I still own the thing they selled, you only need a system that can compare these and see if anything has been double spent. The point is, you don't need a running bitcoin-style blockchain for this. You can achieve the same validity with different means.

[qqii]

Using a bloom filter as a distributed hash means you're edging quite close to a blockchain, the only question your schema now has is consensus - how is work examined for trustworthiness? What prevents network spam?

I haven't puzzled it though but intuitively it feels like you wouldn't be able to achieve the "same validity" (aka you'd have a weaker set of guarentees) without the liveness of a blockchain like system. Whether you agree with what threshold of validity is acceptable is a different matter.