@dalias I concur that, for a small server, it is a risk.
But for a sufficiently large server, knowing that a user followed a link from one site to another doesn't seem to me like a viable route to a privacy violation.
I am also unsure that this is a zero-sum game. Just because I gain something, doesn't mean you lose something. We are both (I hope) enjoying this conversation. I have not lost anything if you are enjoying it more than me.