I think this a brilliant marketing idea, loads of people are talking about coke, I'd love to know what sales of coke are doing currently. I think they will be doing pretty well, will be interested if they show how successful this has been or not down the line.
The EPOS (Point of Sale) Data I see show's that it has worked in some parts of the UK, with a significant percentage steal from other soft drinks, but has not generated a huge rise in base line sales. Scotland has not taken to the idea though, sales of Coke seem to be down - no idea why. Have heard story's that the "Friends" and "Sharing" bottles were introduced to be stocked in Scotland as they didn't like buying bottles without their name on (I have no eviedence to support this, just conversation from Tesco category buyers).
However Tesco and JS have reported many problems with people emptying fittings to find a particular name, and Tesco Metro were considering delisting 500ml Coke variants while the promotion continued as they don't have the staff levels to keep the fitting tidy - believe this when I see it as Coke provide most of the free standing fittings anyway.