"I keep going to Duck.com when meaning to visit DuckDuckGo.com"
Tell them that you called your search engine Duck Duck Go, registered DuckDuckGo.com, and for them to visit DuckDuckGo.com. It's not as though you were ever called Duck.com instead. This just sounds like a petty whinge otherwise. Sorry!
Daniel meant to convey that he hears that line from other people who get to hear that line within their circles of recommendation -- effectively after the damage has been done.
Doesn't sound like a petty whinge according to me though at least if you follow his full explanation of Google actually capitalising on this confusion and redirecting users to their own engine.
Capitalised on the confusion? They have hundreds of domains pointing to their main site. On2.com or whatever it is showed an acquisition notice because that was the company purchased. It's definitely possible that enquiring about the domain reminded them that they had it and should forward like the rest they owned.
Tell them that you called your search engine Duck Duck Go, registered DuckDuckGo.com, and for them to visit DuckDuckGo.com. It's not as though you were ever called Duck.com instead. This just sounds like a petty whinge otherwise. Sorry!