Using frames and iframes to support web 3.0 pages is a great way to simplify the architecture, and avoid the complexity of AJAX. It also makes implementation of a CDN easier.
There are many ways to provide graceful search engine indexing of the pages - using Google’s site maps, Apache rewrite rules, and other creative approaches. Imagine the rich pages you could build, easily. Augment it with sophisticated browser caching and you can greatly speed the pages and reduce bandwidth requirements.
This also supports the idea of micro pages mentioned earlier.