What´s DuckDuckGo secret?

Do you know DuckDuckGo?
Do you want to know their secrets?
I will tell you more, and you will know them more.

Let´s take this quote from FastColabs.

DuckDuckGo's Secret Weapon: Hardcore PrivacyWhen you do a search from DuckDuckGo's website or one of its mobile apps, it doesn't know who you are. There are no user accounts. Your IP address isn't logged by default. The site doesn't use search cookies to keep track of what you do over time or where else you go online. It doesn't save your search history. When you click on a link in DuckDuckGo's results, those websites won't see which search terms you used. The company even has its own Tor exit relay, allowing Tor users to search DuckDuckGo with less of a performance lag.5Simply put, they're hardcore about privacy.
But things didn't start out that way. Weinberg, who says he has "always been a privacy-minded person," wasn't particularly concerned with search privacy issues when he first started building the service. In fact, he knew very little about the matter at all. Then early users started asking questions.
"Some of the first questions I got were about privacy," Weinberg says. "I had launched and it was on Reddit and Hacker News. So it was tech-heavy and there were a lot of privacy-minded people."

Did the site use tracking cookies? Did it log IP addresses? These are things Weinberg hadn't thought much about, but clearly mattered to his newfound user base. So the self-described tech policy geek decided to dig deeper into the privacy practices of Google and other search engines. He didn't like what he learned.
"If you look at the logs of people's search sessions, they're the most personal thing on the Internet," Weinberg says. "Unlike Facebook, where you choose what to post, with search you're typing in medical and financial problems and all sorts of other things. You're not thinking about the privacy implications of your search history."
This common functionality, combined with the possibility for accidental data leaks and hacks, made Weinberg nervous. At the same time, he realized that it was still possible to build a viable business model around search without tracking users. One might not reach Google-levels of profitability without large-scale targeted advertising, but the fundamental logic of delivering search ads--user searches for motorcycles, you show them a motorcycle ad sold by keyword--is still sound. And, of course, the profitability of such a model only grows as more people search more.
It quickly became clear that taking a no-holds-barred approach to privacy would give DuckDuckGo a unique selling point as Google gobbled up more private user data. So the company positioned itself accordingly and started amassing attention as the issue of online privacy slowly ballooned in the public's consciousness.
"It was extreme at the time," Weinberg says. "And it still may be considered extreme by some people, but I think it's becoming less extreme nowadays. In the last year, it's become obvious why people don't want to be tracked."