Yes and No.

You may want to read this post before the OP edits it out : http://www.flyertalk.com/forum/13069064-post7134.html

A FR has been triggered based on his subsequent posts which were edited out already.

And this post someone replied with his own experience :
http://www.flyertalk.com/forum/13070209-post7142.html

It depends on how aggressive a person is doing this, especially whether the person has had OTHER meaningful non coin charges on their cards.

Chase is the latest being reported to close cards 'Not used for intended purposes" with the Mint being the majority charges on the OP's cards. The data point is reported on the coin thread if you want to find it.

AMEX has been looking at the charges closely - yes pts still posted but again, if majority of the charges is from the coins, reportedly you will receive a warning call, followed by request of 4506-T because a Financial Review is triggered. If you dont compile with the request, be prepared to see involuntary closure of your cards. Someone just has experienced such on the coin thread as well as asking questions in the AMEX forum trying to bypass the 4506-T request. Based on his original post, he would no doubt fail the FR. He has since deleted his original posts regarding the FR.

I am sure you understand the meaning of Financial Review by AMEX and its consequence if you does not pass the muster.

There is a long running thread in AMEX forum about credit lines being cut. In it you would find reports related to FR being triggered by coin orders. In fact a few months ago someone's AMEX cards, incl the SPG were all suddenly closed with his wife traveling and the AMEX cards were the only cards she had with her. The poster has started a thread to report this saga. You can do your own search to find it and read thru it.