Well it's just supposed to illustrate an idea but in this particular example the same thing happens as if you were using the database version and the email with the unique code in it was lost: the user has to request another email be sent. The difference being you don't have to go clean up all the unused tokens out of the db.
Yes, I realized just after posting this that he was talking about a specific use case (user registration) where the user is the one making the retry in case of failure..
So his example is OK in fact (a variation on the SYN-cookie), I was wrong.
More generally, that process depends on both the database and network, so reliability is already the min(database, network) => network. It makes sense to eliminate a component if you can.
