[bogomipz]

Also it might be relevant that FB buys third party data:

http://www.businessinsider.com/facebook-data-brokers-2016-12

It wouldn't surprise me if a credit card payment for a doctor visit might lead to such an association or suggestion.

[tyingq]

Ugh. Hadn't thought of that. That means, probably, they are also filling in their social graph for people that have never touched Facebook at all.

[bogomipz]

Right the "shadow graph."

I've also noticed other trends to where using a credit card at a store has resulted in receiving postal junk mail from the store I have just used the credit card at. I suspect credit card companies give give stores access to your credit card billing address when you use your credit card there.

Protecting against these creeping incursions is certainly a feather in the cap of crypto currencies.