Don't fight the Internet. Enhance the user experience.

Definition: Web 2.0 is characterized by social and business connections, the sharing of information, and online collaborations between customers and businesses. Similar to viral marketing which can be defined as, the use of pre-existing social networks to produce increases in brand awareness or to achieve other marketing objectives.

Purpose: The Internet is ever-evolving. Don't fight it. Use the Web 2.0 tools to get your consumers involved...invite them to participate in marketing-related activities from offering feedback to requesting customer service to developing fresh ideas.

Examples:
Blogs
Social-networking websites: LinkedIn, Facebook, MySpace, Twitter
Review (rating) websites: Yelp, CitySearch, MetroMix, UrbanSpoon, MenuPages, Menuism, Blogspot, TheGuide (LA Times), Chow
Video-sharing
Wikis
Online communities

Excellent Article:
The Secrets of Marketing in a Web 2.0 World
From the Wall Street Journal / MIT Sloan
"The authors interviewed more than 30 executives and managers in both large and small organizations that are at the forefront of experimenting with Web 2.0 tools in marketing and came up with a set of emerging principles for marketing."