My mom (again) is subjected to retargeting, but she doesn't identify it as tied to her identity so much as tied to the current search. She uses gmail for work and her personal account (because i set up a google apps account for her), but I doubt she knows that just because she's logged into gmail that google search is tying that information back to her identity.
This is a far cry from Facebook where people know that things in Facebook are tied back to their identity, and not only that is tied back to their identity in a way that may be visible to friends and family.
Both Google and Facebook track you, but Facebook is personal, and people are aware of that fact.
Yes, it's annoying if you're in the 95% of customers who won't actually convert. But it only has to be effective about 1 out of 20 times to be a huge improvement (and that 1 might even be you, but you're mostly annoyed by the other 19 times.)
When you want to search something, do you first go to your facebook account and tell your friends "hey, I want to learn more about x!" and then go to your favorite search engine, and actually do your search?
I bet you don't.
In your example, if the mom is saying "tonight", it probably means that she wants to see it "tonight" (maybe she doesn't have the time right now). so, they should try to make the ad really visible that very night, so the user (this mum) will see it before she even goes to look for it anywhere else. But that would feel very creepy. She would think "how did they knew I wanted that?". It would feel like if someone is spying her. I think the average people is ok to have ads displayed while searching (maybe they will not even notice that some "results" are ads). But when the ads start having a very direct relation to what people posts, they start to worry about their privacy.
What I mean is... sure, facebook could infer the user intention, but in comparison, a search engine has it almost served.