Interesting discussion about the importance and power of 'mash-ups' on the Talent Imitates - Genius Steals blog. Watch the mashed trailer for Spider-Pig. Very funny.
Whether you call it mash-up or cross pollination I agree that it is important to look outside your field of craft or specialisation to move forward. Looking at advertising and design executions I often hear the sound of dueling banjoes in the back of my mind.
It is a serious issue. Innovation is rarely a result of incremental steps forward. Constant research is needed - by which I don't mean focus groups or panels who evaluate the 'quality' of ads or campaigns - but research through constant mucking about and playfulness. The opposite is unquestioning orthodoxy…atrophy and entropy.