[kator]

Yes it's disturbing, again I'm no mind reader, but I guess they assume when you opt-out they just don't map your UID. Meanwhile you're still trackable and just one small data point could be used to reverse everything you visit.

As an example if you sign up for some random blog and they capture UID's they could quickly map your email to your UID and onward into the spiral we go.

IP Addresses are a similar problem for home users, nobody seemed to have noticed that quite some time ago ISP's started making DHCP lease times quite long. Not to put on a tin foil hat, but I assume this was done more strategically then just to reduce load on DHCP servers in their networks.