An unconference is a conference organized on collaborative or p2p principles. While following a variety of formats they generally all break down the definitions between presenter and attendee, organizer and participant.

Advantages

• open exchange - pure knowledge exchange format where providers and consumers of information are free to do and say what they want.
• low organization costs - the costs/effort of organizing an unconference are distributed among the attendees.

Disadvantages

• doesn't readily support driving to consensus or decision making.