DuckDuckGo.com appears to be a Yahoo powered search engine that has just a few modifiers, such as the addition of FavIcons and a Cutesy UI.
Duck Duck Go is clearly looking to capitalize on the Popularity of WolfRam.com in the press.
Everyone wants to see Google Fail, and with Search being a Multi-Billion Dollar business even a .5% market share is enough to keep 4 employees very, very happy.
Much my personal Google Custom Search, Duck Duck has set up filters to remove spam, and has some filters to search specific sites. But there is no “Underlying” tech, this is just stuff Google Should be doing but hasn’t.
I use my Google Custom Search almost exclusively, because it works better than Google, for me. With a few tweaks it could probably work better than Google does for anyone.
DuckDuckGo.com is only interesting from the stand point that they proved how easy it is to get press on Search at the moment. People want to see the Google Goliath Topple.