Wow, two ignorant responses that have NOTHING to do with it... and DINGDING*DING we have a winner.
ChristinaCa was the only person so far who knows what Web 2.0 actually meant. It was simply an observation by some names in the industries sipping coffee, on how certain websites had supplanted older websites about a decade ago.
BUT, ** [people] ** suddenly started throwing the term around -- similar to how today people are using the term HTML 5 to refer to things like the new ECMAScript support and CSS3 as "HTML 5" -- when they have absolutely NOTHING to do with it.
Web 2.0 does not mean "rounded corners and gradients" like the photoshop jockeys claim, it does NOT have A BLASTED THING to do with SEO no matter what the SEO scam artists might claim -- it was just an off the cuff observation that has been perverted by snake oil doctors to once again, prey on the ignorance of others.
... to the point that amongst developers in the know the mere use of the term "Web 2.0" to be an indication you are dealing with someone who probably has no clue what they are talking about; they type of clients who think they can get sound technical advice from the pages of Forbes, which is akin to taking financial advice from the pages of Popular Electronics.
... and really as to your question, as I just said "Web 2.0" has absolutely NOTHING to do with SEO. Since it has nothing to do with code or content, it means nothing.
You know what they call it when you have a term everyone is throwing around that actually has nothing to do with how people are using it, and is ultimately meaningless? "Sick Buzzword"
Web 2.0 might as well be a proactive paradigm...