Like I say in the privacy statement, I only log anonymized info.
"I anonymize the last byte of your IP address with the piwik AnonymizeIP plugin. That means that rather than your IP showing as 18.104.22.168, I would see 22.214.171.124 . "
This gets aggregated monthly which ought to make it more difficult to deanonymize a visit. Be interested to hear if other people can suggest better ways to achieve this.