> anonymize your users IP addresses before sending the information to Google
That's a nice placebo that does almost nothing. Even if the packet body doesn't contain the IP address, it's still available in the IP header's Source Address field.
However, even if we assume Google - in a reversal of their general focus on gathering as much data as possible - doesn't recover the address from the IP header, their own documentation[1] for analytics collection URLs with the &aip=1 parameter (which should be present when 'anonymizeIp' is true) says:
"... the last octet of the user IP address
is set to zero ..."
Zeroing the least interesting 8 bits of the address doesn't make it anonymous. They still get to record the ASN, and they are recording at least 8 bit of fingerprintable data from other sources. I should be trivial to recover mostly-unique users, and calling this "anonymization" is at best naive and for Google, an obvious lie.
Their documentation even betrays their intentions:
"This feature is designed to help site owners comply
with their own privacy policies or, in some countries,
recommendations from local data protection authorities,
which may prevent the storage of full
IP address information."
Actually making the data anonymous isn't the goal. They just want a rubber-stamp feature that lets them comply with the letter of the law.
> ga('set', 'anonymizeIp', true);