There's no doubt that the marketers who embrace the concept of co-branding are giving themselves an advantage in the market.
And the smartest marketers are the ones whose brands get dragged along in the stronger equity and values of the brand they partner with.
McDonalds have done that by linking their products with the Heart Foundation Tick. Great move for Macca's, but not sure that it does too much for the HFT. More and more people are starting to recognise it's not much better than another John Laws Cash for Comment advertorial.
I'm not sure how Prada much is benefiting from their association with LG here...
Then again, some brands do it really well - when two excellent brands combine together to truly enhance each others equity, like Qantas Business Class and Morrisey have done recently.