I am a big fan of Piwik and have been using it for a couple of years now. Today I ran an ad campaign and was monitoring my server’s logs as well as using both Google Analytics and Piwik on the same page.
Piwik is not recording some visitors while they both appear in the log files and Analytics. These are NOT bots but real users some were coming thru search engines.
I think this is a major problem and should be looked at ASAP. I know others have complained about this but I finally have proof that this is happening.
Anyone else having this problem? One way to test it, is to add analytics to the same page and see what happens and then you can check your server logs for any discrepancy between Piwik and Analytics.