John Battelle's Searchblog: Put On Yer Search Hat explains how Don Park has some search ideas: that it would be useful if you could tell the search engine what your priority for the search was (e.g. you're a developer, or you're a home PC user) and that you might have more than one profile and switch between them.
This is actually closely linked to work the TSSG has done on distributed Resource Discovery Systems in the EU-funded Gestalt and Guardians projects.
In these projects the primary focus was on discovering re-usable on-line e-Learning content modules , and various types of XML metadata were used to describe these modules (IEEE LOM and others), and to describe the users, and to describe the devices. The architecture, however, is applicable to pretty much any form on-line content. The public results of the Guardians project can be downloaded from Guardians Public Downloads
The problem with the type of approach suggested by Guardians is the large overhead in the creation of the metadata in the first place. Whilst I am also a big fan of Cory Doctorow's polemic metacrap document warning of the simplistic assumptions about metadata, I also beleive that more sophisticated auto-generated profiles and resource decriptors will help refine the very rough search strategies used by search engines currently. Roll on the semantic web....