Privacy online is a tricky concept even before you introduce online advertising. I'm not talking about surveillance from governments, corporations, or other evil organizations of whatever flavor your imagination can come up with, but what comes up when people search your name or even username.
The reason I bring this up is because once upon a time (recently), I was at school and the person next to me, talking to me, decided to google my name.
Layer 1: Real Name
If one were to google my real name, they would find a facebook account my parents made for me (basically to reserve my name, I think they also tag my face in it though), they would find my old instagram profile, my old blog, my linkedin which I made a little big ago, and until recently a soundcloud account. I don't believe anyone could piece together Robot Landscape or any other alias I use, but you can reveal a lot about me from what you might find on each respective page.
That's rough. I was “friends” but not super close friends with this person, and all the sudden he knew more about me than some of my close friends. Creepiness aside, I probably wouldn't have minded he saw some of the stuff he did, and I would have told him if it came up in conversation. I didn't have control over it though, and if something bad did show up (or he found a way to layer 2) then I more likely would have tried to stop him more than I did.
Layer 2: Connected aliases
Layer 2 I'd consider to be Robot Landscape, and in a way I'd consider it a bit more dangerous since it's not out of reach for people irl a lot of the time, but it's still more brutally honest. The real you shows up, and unless done properly, it could be traced back to Layer 1.
Layer 3: Anonymity
For the sake of completeness, I'll have this one here. You make an account on a random site, and it's not tied to your identity.
Just some things to think about. Robot Landscape