> I noticed one US commentator claiming Cambridge Analytica's Facebook micro-targetting can't be that effective because it didn't work for Ted Cruz
I think it's ineffective because the sentiment of "likes" is murky, and FB is full of fake names and demographic info. On political topics, real people's sentiments may actually be lost in the noise from shills and bots. There are loads of data-bombing antics as well: "Boaty McBoatface" and "Penis Flood" and "Hitler Did Nothing Wrong" to name a few legendary ones.
OTOH it's a goldmine for targeted advertising, phishing, and stalking. Friends lists, contact info, birthdays, favorite brands, interests and obsessions, embarrassing photos, drunken comments, etc.
For what it's worth (you can find this on Fox, Breitbart, etc) the Trump campaign claimed it didn't work for them either. They only bought the CA data because the RNC establishment denied them access to its voter data... until a month before the election. They tested both datasets, found RNC's to be much higher quality, and never used CA's. So they claim.