Until I change just one of those identifiable metrics, that is, right? As soon as I change, for instance, my screen resolution I am another unique user and am no longer identified with the previously unique fingerprint.

Surely, if someone installed insidious software on every single page of the internet and tracked me everywhere, there could be a way to use some fuzzy logic to re-identify myself. But we're way into the deep end on hypothetical again, right?

My main point is that, practically speaking, it isn't very.