Is big brother watching you on the internet?

I have been wondering about being watched on the internet lately ever since I overheard some knowledgable people talking about being marked for life and things like that. I wonder, if someone partakes in illegal activity on the internet, are they in danger from it from then on? Do the tracks fade with time? Is big brother watching? I go on /b/ a lot and just being around some of the stuff that goes on there is enough to make me afraid of the 4chan party van.