Since I am still bringing all my content together I thought I would pull in this post from Quora asking what is special about DuckDuckGo.
Privacy enabled by default. This certainly helped get traction when the NSA security revelations came around. DDG is not the only privacy conscious search engine but certainly one that pushes it as a feature more then others. See https://duckduckgo.com/privacy
!bang syntax. Remember back in the early days of Google they had a “Try this search on” and a list of search engines? !bang is that idea on steroids. This makes the cost of switching to DDG much lower then any other search engine because you are not locked in when its results are lacking.
Gabriel Weinburg (Creator) came up with a way to index the web for a fraction the cost of anyone else. I.E. use someone else’s index through web API’s such as Bing/Yahoo Boss. This means DDG can have an index in billions of pages without buying hundreds of machines and then crawling and indexing. Consider Cuil as an example. BTW I wrote more about this here Building a search engine? The most important feature you can add.
Persistence. Quite a few search engines based on Yahoo Boss and other API’s have come and gone, however DDG continues to be worked on. Just being around for 4 years gives it credibility.
DuckDuckHack. If you are a developer you can go to DuckDuckHack and add functionality you want. This may not sound that good, but because DDG already has traffic its a good incentive for start-ups and others to build on the DDG API to get some traction, which means they want to use DDG and promote it which fuels growth.
People. The people working on DDG are pretty awesome.
Uncluttered results. The results are pretty much just some links without too much fancy stuff going on.