While I prefer advertising to having to pay half a cent (or whatever it would cost) a page to view sites on the internet, there are some behaviors that annoy me. Some sites use cookies in an attempt to harvest data and predict what kinds of products I wish to hear about. They have their own problems, but at least they are focused on the actual computer. Other sites appear to track IP addresses, leading to a very annoying problem.
When cookies are local to the computer in question it is possible to disrupt them somewhat by removing the unwanted cookies and using browser modes which at least attempt to limit them. While they can be more detailed, the important thing is they only affect one device (unless something like a social media app with a login gets involved). This means that unless the computer is shared, the tailored ads only appear on that one computer.
Now we come to the problem with what I assume to be IP address tracking: gift buying. I search for the gift in question. Then suddenly every computer/tablet/phone in the house suddenly starts showing ads for that product. There goes any chance of a surprise gift. Very annoying.