Why Web 2.0 websites have higher PR?

Well there is no direct reason why a web 2.0 website comes higher on PR.

But there are implicit reasons why web 2.0 websites rank higher. I could think of followings

1) C2C (Content to Code ratio) is higher in Web 2.0 websites as they use CSS and no tables. This certainly has an advantage over traditional websites with tables.

Search Engines do like a clean code ain’t they?

2) Web 2.0 designs are attractive and they really do attract visitors more than traditional websites who often bookmark these websites or refer to others or circulate among their friends who in turn bookmark/refer and this whole chain goes on.

3) With pure CSS the websites pages render faster by virtue of having less code and not to mention that Google now consider the speed as one of important factor in SEO.

To sum up I would say that even though there is not direct relationship between Web 2.0 and higher PR but in the background a web 2.0 design is bound to get notice not only by humans but also by search engines. A Web 2.0 design certainly helps you in Search Engine Optimization to achieve Google top 10 Ranking.