If you read the reports , specially on flyertalk,
http://www.flyertalk.com/forum/credit-card-programs/1465023-citi-cards-closed-perk-abuse.html you will find daily reports of Citi card shut downs, Many for large spend & some for specific store purchases.
Once they shut down one card, not only they take away the points, they close any other cards with them.
For example, if they close your TY card, they close your Citi AA and other citi cards you have.
Some got their TY card closed for redeeming points for mortgage & student loan. They also put a stop payment on those checks.
I have over 70k thank you points on my TY card. I received 10k points offer for $3k which I did last month. Before that I rarely used my card.
I don't have plane tickets to book. There are no Amazon GC, I wonder what to do cos I don't want to lose my points.