I have now tried to implement the Criterion myself, bascially using the decompiled code from EPiServer.Personalization.VisitorGroups.Criteria.ViewedPagesCriterion. It turns out that the criterion subscribes to a VisitedPage event which is supposedly raised when a page is visited. By debugging, I have determined that the event subscription is successful, but the event handler is never called. This means that, for some reason, EPiServer does not raise the event.

I tried to subscribe to the StartRequest event instead, and in this case the handler is called. This begs the question: Why is the VisitedPage event not raised when visiting pages?