Surveillance is possibly the worst of the bunch. They say it’s just to do a better job of serving ads, but that’s only the tip of the iceberg. Governments could easily use it to know and track everything you do online. Just wait till the next elected nut job wants a list of everybody that has ever looked at or searched for a certain type of information, maybe they don’t like that you looked up info on abortions or lgbt info, now they can know the full extent of what you saw and when.
Ads will be worse. You think YouTube ads are bad now, just wait till you can’t visit any page without the mandatory viewing of their ads. They can require a cam installed to make sure your eyes are on the ad, helpfully pausing the video when you look away.