The main issue I have is with duck.com. A lot of people remember that we are a search engine "duck something" and so naturally try duck.com. As a result, there is a lot of confusion, e.g.:
"I was telling someone about DuckDuckGo and they thought it was Duck.com and they went to Google. Is Google using this to find people who make the mistake to Duck.com instead of DuckDuckGo?"
"Can't you do something about this? I keep going to Duck.com when meaning to visit DuckDuckGo.com They are using the DuckDuckGo name to get people to search Google."
This only started happening after I asked about the domain name. It used to point to a history page about Duck Corporation (previous name of On2 -- http://web.archive.org/web/20100802014055/http://duck.com/), similar to http://www.on2.com/, which was acquired by Google in the same acquisition.
Google should legitimately not sell it to me, though it would have been of course nice to do so when I first asked in 2010. I think an appropriate remedy would be to either point it nowhere, point it to the original page it had been pointed to for many years, or point it to the acquisition page (as http://on2.com still does) -- all things they do in other cases if you look at past acquisitions.
Just to be clear, it is only anti-competitive because it causes confusion, and relates to their core search product. The facts of the situation (that it switched shortly after I asked, and only seemingly that one domain) make it appear to be deliberate. And if it were not deliberate, I've brought this up many times and there has been ample time (including now!) to correct the situation.
With regards to being easy to add search engines to Chrome, see http://www.gabrielweinberg.com/blog/2011/02/usability-issues.... I've written up the differences extensively, with screenshots and explanatory notes.