There is the problem of relevance - you must order your search results by relevance, Now you can have one global model of 'relevance' or you can have several mo

There is the problem of relevance - you must order your search results by relevance, Now you can have one global model of 'relevance' or you can have several models (i think the web is so big that one model is not good enough). relevance can be relative to language/origin ; number of links away from a wikipedia article ; coolness (has it a link from a known twitter account/news aggregator) ; age group ; a link from HN frontpage or slashdot would make it 'nerdy', news - was it referenced by a news source etc. etc. I think a differentiator would be to have a non intrusive and intuitive UI to select an available relevance model (instead of trying to profile the user based on his search history / browser history) On the one hand the user profile is of great value for advertising, but on the other hand the explicit choice of relevance model can be used to match relevant adds.