After my mom (who has no relationship w/ Amex) received an offer of 50k MR points for spending $500, I complained via email to Amex given that I have both the Premier and SPG amex cards (combined spend of $3-4k per month) and only received 15k MR bonus points.

In the past, this would have resulted in a "too bad for you" type of response or a token 1k or 2k bonus MR points. However, this time Amex responded within 2 hours of my email and posted an additional 20k to my MR account. While it was not the 35k difference, it was a pretty good gesture on the part of Amex and I intend to keep the cards.