Most people are going to use Google, maybe Bing, maybe Bahoo!, and are barely aware of and would not use another search engine.
Those that do know about DDG will either use it or not.
Whenever I include a search link in an email (or HN thread) it's always a DDG link, except for those rare searches where I get nothing back from DDG. I think that's one of the best ways to promote DDG. Bonus, the DDG search links are unadulterated.
https://duckduckgo.com/?q=duck+duck+go
Firefox, Ubuntu plus whatever 2 or 3 way deal Google has with all that:
http://www.google.com/#hl=en&cp=6&gs_id=11&xhr=t...
Chromium, Ubuntu, plus whatever deal ...
http://www.google.com/#hl=en&cp=6&gs_id=m&xhr=t&...
I didn't ask for that, and I would have to clean that up before I pasted that google search into an email.
Opera etc:
http://www.google.com/search?q=uzbl#pq=philadelphia&hl=e...
And by the way, if you want to search google a little more anonymously, do it via DDG. In your search bar or on DDG's page, type in !g your search term. You'll be redirected to Google's search, and the URL will be relatively clean:
From ddg, !g duck duck go gives you:
https://encrypted.google.com/search?hl=en&q=duck%20duck%...
I still didn't ask for the hl=en bit, but it's much better than the cascade of line noise that Google would otherwise give you.
Edit: minor wording.
I have no idea if Google is still trying to stop people doing this or not.
Google used to (still does?) send cease and desist letters; and they've asked people to only use google-as-a-verb when people are actually talking about Google. Thus "I'll google it" when a person is using Bing is, according to Google, not on.
I also encourage people to submit feedback with specific result issues.