I was going to ask how a remote pckg could do that. Not knowing how rust works (or package managers apparently) I didn't understand how it could be widespread. Makes sense, damn; that's substantial.
I'm not sure how other package managers do it (it should be noted that this approach was designed to avoid some problems that other package managers have encountered), but there is still room for improvement here: ideally, I think we'd be hashing crate names rather than storing them verbatim on the filesystem, to enforce more uniform distribution in the trie.