Old Jul 19, 19, 7:08 pm
FlyerTalk Evangelist, Moderator: American Express, Citi, Diners Club, Signatures
Join Date: Jun 2003
Location: Miami & London
Programs: AA & Marriott Perpetual Platinum; HH Gold
Posts: 38,374
The first report/complaint that I recall was in 2011 with American Express:

Amex tells Amazon if you are Membership Rewards Member

Further discussion in 2015:

Amex selling rewards points data to Amazon?

I believe Citi has the same arrangement with Amazon.
mia is online now