For your example of youtube videos: Links of videos are often shared and I would expect that Google already developed something like "propagation graphs" between google accounts. There is a substantial amount of mony behind youtube views and much effort is made to guarantee that the clicks are real.

Any manipulation should be plausible and match with your remaining data.

You forgot Facebook and Amazon. Most data is now collected from your smartphone via behavior analysis (location movement,etc). This hard to fake. You should also expect the data is used by intelligence. Deviations of the norm put you on a list.