It is an attack on privacy. The recipients don't expect to be tracked in this way, and you don't ask their permission before doing it (1). You're exploiting a weakness in the system.
It doesn't matter how many organisations are doing it, or how long they've been doing it, or how much money they make from it, or how useful the information is, or how good the "services" you provide are. It's still an attack on peoples personal privacy.
I don't expect to be able to convince you though. After all, you work for an ESP so you have to justify it to yourself somehow.
(1) hiding something away in the T&C's doesn't count.
EDIT: Oh, are you talking about tracking someone on your website, or tracking people across websites?
EDIT2: When people visit a website, they expect that website to be able to see their IP address and track their movements across it. What people don't expect is that websites (without their permission) can track their movements across other websites.
It doesn't matter how many organisations are doing it, or how long they've been doing it, or how much money they make from it, or how useful the information is, or how good the "services" you provide are. It's still an attack on peoples personal privacy.
I don't expect to be able to convince you though. After all, you work for an ESP so you have to justify it to yourself somehow.
(1) hiding something away in the T&C's doesn't count.