“We are sorry, but this can’t be done.” I hear this from most of the creative and innovative agencies whom I approach for executing marketing strategies. It’s not that they can’t execute it technically. Its purely a psychological thing.
Side Note:
Just because you haven’t done it before, does not mean that it can’t be done. Intention becomes paramount.
CachedIdeas - Ideas on the Go! 
may be it varies depending upon da situation