While I dont 100% agree (some codes are pretty clear they are for Ambassadors or for Elites) many codes are indeed published all over the place including hotel literature and Priority Club Insider. While I appreciate from looking through the fine print that Priority Club Insider is not in fact associated with IHG it seems to me that many casual observors (ignoring the hard core FT'ers and AFF'ers for a moment) may well have enrolled for promo's thinking they are totally legitimate and have been penalised.
In an internet savvy world published and publically available may mean somewhat more than IHG intended but that doesnt mean they aren't indeed published and publically available, and IHG has done nothing as far as I am aware to ask these websites to remove these codes.
No doubt FT'ers will be talking about a class action, I'm not a fan of legal action in general but this is one case where I do think IHG's behaviour in this regard has been unconscionable.
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