Joshua Porter elegantly discusses the tension between aggregation in general (search, webfeeds) and designing information architectures. In short, aggregation routes around home pages. Home page. What a quaint concept!
Maybe IA designers should start thinking of sites as rings, layers, semi-permeous borders? There may be an aggregation attractive fringe and then a less amenable core. Alternatively, ever page can be a "home page". Either way, thinking regarding the structure and interface of a site becomes markedly different.