Blekko is a search engine that combines human curation and the ability to dynamically filter results with "Slashtags" to provide high quality search results.
Pro Uses human curation to provide better results
Blekko believes by adding a layer of human curation on top of search results, quality can be improved. It makes sense, no algorithm can be 100% perfect on the near infinite breadth of search queries, so allowing people to curate the results to remove bad results and promote the best is a great solution. Blekko pulls searches from a list of over 3 billion trusted webpages.
Pro Slashtags allow searching through a curated list of sources
Slashtags allow limiting the search to a set of trusted websites. Blekko has hundreds of slashtags across various categories that are all human curated. The Slashtags also help with discovering content in a particular category.
Pro Provides context to results
Blekko by default categorizes answers in boxes such as tech, social, or news making it easier to understand what's the context of the answers in each of the categories.
Additionally, the curation of websites and slashtags allow Blekko to provide context to results that may have multiple interpretations or when you want to find a particular type of information on a given query:
Pro Effective at removing "content farms"
Arguably doing a better job at removing spam and "content farm" websites than Google.
Blekko have managed to be very open about all aspects of their search engine.
Con The interface is a bit cluttered
The redesign of 2013 added automatic categorization, but the design feels a bit cluttered since that change.