At blekko, we believe that the index is the core of any search product. It is the only place where a search engine can provide editorial differentiation. Consequently, we have 1,500 servers that crawl the web continuously to make sure blekko has an up-to-date, relevant index from which to serve results.
It is our goal to serve results for all queries from our own index. Our current index size sits at around 4 billion pages. While it grows every day, the web is much larger than this. As a result, sometimes we turn to third parties to help us return the best results. You can access some of these third party results directly by using specific slashtags, such as /twitter, /facebook, and /bing. But just like we do with our own slashtags, we sometimes blend them in to enhance the search experience.
Third Party APIs that we use include the usual suspects that you would expect to see: Amazon, Bing, Facebook, Flickr, and Twitter; as well as more specialized sites such as Carfax, FedEx, Indeed, Rotten Tomatoes, Truveo, and USPS.
We will continue to seek out the best ways to improve the search experience on blekko. But rest assured that the heart of blekko will always be its own index.