A couple more complications:
Larger organisations generally require their employees to access the Internet through proxies to stop them idling their work hours away on social media sites and other distractions.
IPv6 is an altogether more sensible approach to IP addressing but there are strong business reasons not to do it in a large organisation to do with the cost of changing zillions of devices on desktops, under desks and in cupboards that could stop working and would interrupt business. Large companies do not really manage the IP addressing of their devices on their internal networks very well. It will be long time before they migrate to IPv6.
ISPs are different thing, they tend to manage their addressing much more tightly because they live and die by the integrity of their network, so they look after it, keep all their logs tidy. They will use IPv6 internally and IPv4 gateways for their customers.
However, that is at the IP level. For someone running a server, the information in the http request header and the cookies left in the browser from previous visits is generally enough to identify the end users. The IP address is a useful identifier if it just coming from a regular ISP and a domestic or small business account.
There are, of course, techniques for disguising all this information and making it deliberately misleading. If you want to watch the BBC in Spain, the UK expats know all about proxies that change your apparent IP address. Same with Netflix, the selection of programs is much wider if you have a US subscription and IP address. The Chinese are also well versed in the same techniques for political reasons.
If it were possible to accurately track large numbers of users from their IP address and browser characteristics, we would have far better targeting of ads with relevant material.
I am not seeing the signs of this happening if I switch off my ad blocker and look at the selection of ads a website shows. It is all over the place and very annoying.
We have not quite reached the level of surveillance suggested in ‘Minority Report’, no matter how much the sellers of advertising may wish it were so.
PR interns doing amateurish hacks of Wikipedia for political lobbyists are probably quite easy to spot with a practised eye.:dubious: