Can you have a way to track how many people registered, were prompted to pay a fee, didn’t pay, and subsequently registered a different account (both that did and did not require a fee). Something other than IP address would need to be used to track this.
That would go against many things this forum stands for.
Further reading:
A year or two ago I was researching fingerprinting techniques that'd work against pretty much anyone with JavaScript enabled, and I found several promising leads on that front. But then it occurred to me that I don't really want bitcointalk.org to be known as the #1 forum on the leading edge of de-anonymization technology, so I stopped pursuing it seriously...
It is not necessary to rely on NSA (or Chinese government) level spying to track what I was referring to. I was referring to something closer to
tracking cookies that can track your activity. I believe these can help detect things like if accounts are being hacked, for example if someone is accessing an account with the same browser type and IP range as normal but without a cookie that has previously been consistently present when accessing an account. I also believe these can pretty easily be removed, so if you don’t want this type of tracking, it is trivial to stop it.
I believe there are other types of tracking that doesn’t require NSA level spying.
The quote you cited was referring to very advanced tracking when the person being tracking is taking many steps to avoid being tracked. I don’t believe even the likes of Google and Facebook employ the types of tracking referred to in your quote.