Wikipedia is almost already a blockchain. All they need to do to become one is to add a cryptographic hash of the previous database backup to a page included in the backups. (This is what git does when it inserts the parent hash(es) into the commit metadata, and it is a generalization of block chains —it’s “chain” is actually a set of directed acyclic graphs)

Anyway, wikimedia posts backup copies of the database at dumps.wikimedia.com, and those pages include sha and md5 hashes. I even found a page of magnet links for english wikipedia on the meta wikipedia.

Magnet links contain the hash of the target, but it’s unclear if meta.m.wikipedia is included in the english language dump file, or if it includes magnet links pointing to itself.

I’d love to find the missing links. I’m sure Jimmy Wales would love credit for accidentally reinventing the blockchain before the term was coined.