Business worldwide has gone through extensive consolidation and globalisation, so that many B2B companies now find that a very few huge customers contribute a crucial amount of their turnover. For them, key account management (KAM) is marketing, or effectively all the marketing that matters. Even companies with a more balanced customer base recognise that they survive or sink depending on their top 20 or 30 accounts. This degree of focus has inspired them to develop customer relationships that should be the envy of consumer marketers. Obviously there are major differences between relationships with consumers and those with key customers: scale being the first to mind. Nevertheless, there are elements in KAM that, even if not directly transferable to relationships with consumers or smaller B2B customers, should prompt some hard questions for interactive marketers. B2B suppliers to giant customers have learned some expensive lessons, and it is these that this paper seeks to pass on to B2C marketers, so that they can avoid some of the pitfalls and develop realistic CRM strategies. The paper shows how these key relationships can be classified in order to distinguish between them and the strategies that can be applied in them. It concludes that when relationship building is warranted, which is not with all or even a majority of customers, the supplier needs to be very clear that they have selected the right customers, who will be responsive and give an appropriate return on investment. The findings discussed here are underpinned by the research into KAM carried out by the author on behalf of Cranfield School of Management.