However, from a less technical perspective, the Tim O'Reilly general session opening keynote and subsequent panel discussion drove home the idea that "Web 2.0" is really about collaboration, and that "collaboration" can take multiple forms, not all necessarily intentional. (A tag cloud, for instance, reflects the activity of multiple people, and improves as more people "contribute".)
Tim also touched on the area of data accumulation, and how it behooves an application not to simply collect data but to provide value to the end user based on that data. Example: if Google were the phone company, they would likely use your call record to build an automatic phone book for you, most-called-numbers first. What does your current phone company do for you with all the data they have on you?