I was reading the post on Google's blog that Caffeine has now definitely gone live (http://googlewebmastercentral.blogspot.com/2010/06/our-new-search-index-caffeine.html) and it mentions that there is now a much bigger emphasis on fresh content. it looks like they want it in the index as soon as it leaves your pen.
I'm thinking that this might explain some of the crazy SERPs we've been seeing recently. If it's being dropped into the index straight away, then that obviously means that external links no longer play so big a role in weighting a page - because the new stuff won't have been given enough time to gather any deeplinks before it ends up in the SERPs.
the only way they can weight the fresh pages is through a combination of links to the site as a whole (that old 'authority' thing) and user behaviour. but even user behaviour is not much use when it comes to new pages. because they're not going to want to wait half-a-day to collect it. they want it in the index straight away.
the only other thing that remains to help them rank the page is... old-school on-page factors. keyword density, titles, alt tags, internal links, that kind of thing. i remember reading in another thread how people have begun noticing internal links having a benefit. maybe they are right.
i reckon what we are witnessing here is old-school SEO making a comeback.
