In the rapidly spinning world of multichannel marketing, both the marketers and the service providers are struggling to define what multichannel marketing means and how it applies to them.The one point most seem to agree on is that this is a world without channel walls. It's a world where communicating directly with people in the most effective way, and allowing them to respond the way they want creates the most trusting, enduring relationships. And performance bears this out every time. (This article was originally published in the January 15, 2007, DMNews Essential Guide to Lists, Database Marketing and Data Services.)