The only thing I take umbridge with is the "close or downgrade within 12 months" in their sole discretion. Plenty of legitimate users get a new product, use it for a year and decide if the benefits were worthwhile.
I'm only 6 months into my first year with a Platinum card and I'm not completely sold. I signed up at a $450 AF and now it's $550 for a Platinum, and I have only used PP twice, so maybe I don't get that much value out of the card. Now if I cancel for legitimate reasons, I have to worry about them clawing back the bonus?
I think it's shortsighted to have that terminology in there. If 50,000 MRs is the acquisition cost of new business, let them take the gamble. I get why no company wants to pay out the bonus to folks like TPG readers who are just gaming the system for flights. In Amex's history though, isn't the welcome bonus roughly the value of the AF?
Ultimately, the card needs to be used for Amex to make money. So the way I think it should be done, is they should increase the annual spend but spread it out. For example: "Spend $2000 every three months in the first year. Welcome bonus will be applied after six months but may be forfeit if the periodic spending requirement is not reached before the renewal, cancellation, or downgrading of the card."