For the sake of argument though, why would anyone keep the SPG AMEX card and pay a $30 annual fee when they could just cancel and reapply a couple months later with a first year fee waiver and new sign-up bonus of up to 10,000 points?
I recently canceled my SPG AMEX account not because of the annual fee but because of AMEX's refusal to ever target me for double points promos.
Incidentally, I did try to see if they were willing to throw some SPG points my way to get me to keep the card (mostly as a test because I really did want to cancel, barring a really rich offer) and they offered absolutely nothing.