One of those rare times that you think that marketing might actually build a business, rather than just build a brand. The collaboration between Marmite and Guinness is not just a cracking idea that has got people talking - not to mention cool-hunters beating a path to the nearest Harvey Nicks to get hold of a jar and eBayers trading the stuff in a frenzy - but has likely created a whole new market.
It's pretty rare that a marketing agency comes up with something that really changes a client's business and turns cost into profit-centre - Tango men is the last one that we could remember.
Now, the IPA is rewarding the businesses that have pulled off this most marvellous of feats. See the nascent IPA Strategy Blog for details. Be interesting to see what the ideas are that this competition pulls to the fore.