What are web 2.0 marketing techneques

The most important thing is not dissimilar from conventional marketing. It's important to have an understanding of what your audience wants and how you can supply it.

Using 2-way channels like blogs or social networks, you can try to develop a conversation about your product. Find out where your potential customers hang out and engage with them. Comment in blogs or social networks, send messages, create videos and other valuable content and send trackbacks.

What Christian said is spot on. Your message has to make people feel they are benefiting from the engagement and they aren't being sold something.   

When Social Network users (facebook, myspace etc.) spread buzz, it's the internet equivalent of 'word of mouth' advertising.  Having a product or service that people will recommend to their Web 2.0 friends is, I suppose, a technique.

Dave - www.relaxseo.com 

There are a lot of different types of sites within Web2.0 - the social news sites like Digg/Fetch/Mixx/Propeller etc. 

The social networking sites like Facebook/LinkedIn and

Social bookmarking sites like Del.ic.ious/Mag.nolia. 

All of them take different strategies and tactics since they are very different sites.  The one thing they all have in common however, is they require good content from YOU to be effective.   

Even the networking sites need for you to flush out profiles and contribute good info so when you join groups and "mingle" you'll attract leads and interest.

 This is a very good article on Web2.0 strategies... http://www.infotoday.com/mls/mar07/Fichter.shtml

 Good luck!

This is :) Yedda, Facebook, MySpace and everything similar.