I agree.  People aren't (yet?) aware that Facebook will be able to see, extract and analyze the items in the Diem ledger.  And they will do so.  They're salivating about it right now about the information and power that will accrue to them by doing so.  They won't just know everything you like (and by implication dislike), exactly who your friends are, see when you visit just about every web site on the internet and everything they can calculate by implication.  They will know ever site you go to, when you get there, what you do there, how long it took you to actually purchase something, exactly where those funds came from, exactly what you purchased. 

Facebook and their partners will know just about everything about everyone who uses Facebook and Diem.  You want any privacy?  Don't buy into Diem, and delete FB.  The reasons everyone has mentioned above also are relevant.

You buy a hat supporting person X, or a want to donate to person Y?  If Facebook doesn't approve, they could easily shut you down.  Or they could take the coins of the people you are buying from and you'd have no recourse.  Unlike a credit card company which is (theoretically) on your side, Facebook is only on their own side.  Freezing the coins is enough, they already have the cash you used to buy them so if they are frozen, you'll never be able to redeem them while FB has your cash to use as they wish.  Look at how PayPal has done things with frozen accounts. 

This is also why privacy upgrades to bitcoin are so important so that every person every where can validate the chain, but they can't know that person A bought Z from person B.

Diem/Libra is evil.  Could it help bitcoin and decentralized coins?  I am not sure who is stupid enough to turn over their entire life to a company.

Of course, I didn't think in 1993, 1994, 1995, 1996 that anyone would allow tracking of them like Google et al do, let alone like FB does.  Makes me think of the HL Mencken's (slightly edited quote): "No one ever went broke underestimating the intelligence of the ... public."