[troels]

No, but the identification relies on a cookie placed on the 3rd-party site (leadlander.com). With that domain blocked, there would not longer be a way to identify the user across different sites, which is a key element of this thing working.

[d_j_s]

That's not correct, you as a user run a snippet of leadlander js code on your web page. This code has no access to the cookies on a leadlander domain.

I've worked on a similar tracking snippet/system for http://www.projectcounter.org/ and this was one of the first things we attempted.

If you block the leadlander domain(s) the script will obviously not run and also consequently won't be able to send fingerprint details back.