Jakob Nielsen posted in May 2009 an article called “Top 10 Information Architecture Mistakes” where he states that mistake no 2 is not having an integrated search with the structure of the site. I’ve seen many sites that don’t have this integration at all – such as Wikipedia where the articles don’t have relations (through hierarchical navigation). I think it is perfectly OK not to integrate every article on Wikipedia in a monstrous hierarchy which leads to navigational elements. There is a hierarchy on Wikipedia, but not prominent enough to use as navigation.
But there are other sites where this make sense, such as the documentation of Microsoft .NET platform. The navigation is hierarchy dependent in my mind and if there is no hierarchy there can be no integration of search into a structure. In these cases I support Jakob Nielsen’s statement:
Sadly, search and navigation fail to support each other on many sites. This problem is exacerbated by another common mistake: navigation designs that don't indicate the user's current location. That is, after users click a search result, they can't determine where they are in the site — as when you're searching for pants and click on a pair, but then have no way to see more pants.
Still, that doesn’t mean that Wikipedia made it wrong. I must be missing something here, please let me know what?!