With data warehousing, customer relationship management and other technologies, marketers today are able to generate one-to-one personalized messages that dramatically affect the bottom line. 
It is a fact that customers today have less time to shop and therefore demand more from their e-mail subscriptions.  If e-mail marketers are not generating relevant content, customers can remove themselves from a business' only free tracked channel with a single click.
There is something that can be said about batch 'n' blast techniques if you subscribe to the more-sends-equals-more-revenue theory of e-mail marketing. However, until marketers harness the power of the hidden gems buried deep within the data mine, they run the risk of stale advertising and customer fatigue.