[AmericanChopper]

I’d hope not. From the company’s perspective, there’s never any guarantee at all that an IP is going to be 1:1 to a real identity. IPs will be dynamically reassigned to new consumers constantly, and there are many situations where you’ll have many (some times very many) users sitting behind the same IP. The only situation I’ve come across where some level of PII has been retrieved from an IP are services that will be able to link an IP to a particular company’s office. I’ve seen that used in Account Based Marketing funnels where you can get information that ‘somebody at ACME Corp viewed these pages on your website’.

[scott00]

Trackers don't care if they're wrong some of the time. The prediction problems they're using the data to build models for are pretty noisy anyway. If using inexact identifiers improves their model, they'll get used. Many technically dynamic IPs change only rarely... I think my home Comcast IP has changed once in the last 2.5 year. So the correlation between a Comcast IP and a perfect household identifier is going to be pretty good. If you have a dataset that's got search history timestamped and labeled with IP, it's probably pretty easy to figure out the physical address that goes with the IP from map searches. Cross-reference an address to name database and now you've got a dataset with each household's (labeled by name and address, with some error) search history.

[dmitriid]

From a company’s perspective a person uses only a handful of IPs most of the time: home and work.

Combine that with cross-site tracking and phone companies selling your info...

[AmericanChopper]

From a companies perspective, almost all global mobile users are behind cgnat, a huge portion of homes are too, and offices have hundreds or thousands of people exiting from a single or a few public IPs.