DuckDuckGo is a relatively unknown search engine but its ardent users compare it to google.com and even consider it a viable google.com alternative. I have used it sometimes but I haven’t yet formed an opinion. This DuckDuckGo link says that overall 10 billion searches have been carried out on DuckDuckGo. The anonymous searches, as you can see in the graph, have seen a marked increase especially after the revelation made by Edward Snowden.
DuckDuckGo was launched 8 years ago but it experienced an accelerated growth in 2013 when Edward Snowden revealed how the US government was spying on people when they used the Internet. All in all, the above link claims that the DuckDuckGo search engine has facilitated 10 billion anonymous searches and 4 billion anonymous searches happened in the last year alone. On January 10, 2017, the search engine accommodated 14 million private searches.