Yeah, it's a good test - I'll give that a whirl...

Im not sure, but I know facebook will put ads about things you talk about. 
Its more fun to do with a friends phone because they shouldnt be looking up the same thing. 

Satosora

Really?! Is it hidden away in the OS T&Cs? Seems an overreach to be able to eavesdrop without making it quite clear that's what's happening.

486DX2

conspiracy

Do our phones secretly listen to us?

its not a conspiracy. 
They do listen and post things you would look at. 
Try it as an experiment sometime with a friends phone. 