I have one question, are they consuming other companies search API, let’s say Twitter or are they crawling and aggregate their own data? Either way it’s a great job!
e.g. for Twitter, are you crawling all the Twitter users' URLs (seems difficult to do - how do you find new accounts' URLs?), or are you fetching results from search.twitter.com ?
In its current form, most of the results are from Twitter which doesn't really differentiate it much from Twitter Search.