In multiple client accounts, we've recently seen large gaps in the activity data between people who clicked links in emails (Click Email) and then had no corresponding activity logged for visiting the web page (Visit Web Page) of the very link they clicked on.
This has occurred both for Marketo landing pages, and pages (with Munchkin code) hosted elsewhere.
Marketo support suggested these discrepancies could all be chalked up to security sniffs by the email clients, but based on the timing between delivery & click, I don't believe that covers all the cases.
One other clue: in one of the clients, many of the users with missing Visit Web Page activity also had no values for the Marketo inferred fields.
Has anyone else seen this problem, or have any ideas about possible workarounds? Accurately measuring the pages visits is important.