Online privacy is one of those things few people understand. Things change too quickly due to technology or the policies of businesses we interact with (Google and Facebook are good examples), so people tend to ignore the issue hoping everything will be alright.
However, once you realise that advertisers know way too much about you, you do become paranoid. I know I am.
For those of us on the paranoid camp, there are a few extensions and plugins that help prevent companies and advertisers, from tracking you.
I suggest you do a bit of research on the topic of online privacy and take it seriously.