Google and Bing are very good at what they do, but there are certain articles/how-tos and such that I find very useful to keep around without having to remember the exact query I used to pull them up on Google. Also, search results change over time, so that blog article I loved might not score on the search engines like it did last year.
Bookmarking sites also offer some of the functionality a site like HN does, with popular/recent links coming in over time.
That's what I think is important, anyway.
Also browsers have great autocomplete. If I want to go to hackers news. I hit "n" in the url bar and I am there.