I find it hard to believe IHG would boot anyone purely for signing up for multiple promos - I actually doubt this is against any T&C. Many many members of this FT forum as well as blog readers routinely register for everything under the sun but stories of account termination are quite rare.

Did OP by any chance have another account with IHG? Perhaps requested too many price matches? Resold award rooms? Run quiz registration a few thousand times? There are many ways to run afoul of T&Cs but generic promo registration is unlikely to trigger it by itself...