Respecting the Do-Not-Track preference of visitors is something noone must do. It has to be respected, per definition, only by choice of the site owner.

In Piwik's settings > Privacy - Tab, one can choose to respect or not the visitors preference of Do-Not-Track. When one chooses to respect it, "then Piwik will not track these visits.".

To completely not track a visitor's access has quite some impact in the site's popularity estimation; especially since Microsoft sets it against all odds to "Enable" in their Internet Explorer, which is still quite popular.

I'd like to have the possibility to do a mixture of respect the visitors privacy and still at least see the full impact to a site. Isn't it possible to add the option to when a visitor decided to not being tracked, that user's access and all his way across the site is still tracked, but automatically anonymized by not storing the last byte of the IP address for that user, just like "Anonymize Visitors' IP addresses" would have been activated?
This would cover the case that one wants to store and see the whole IP address in the records usually (that's why "Anonymize Visitors' IP addresses" isn't set to yes) but still wants to respect the Do-Not-Track enabled visitors choice without not seeing those visits at all.
Keywords: do-not-track, anonymize