I agree, a non-IT person goes with the default, Bing. Unless they accidentally installed Chrome (which given the way it leaches onto other downloads is pretty easy).
On the other hand my dad (who is vaguely IT literate) actively installs the Yahoo toolbar! It's the first thing he does for whatever reason, and no amount of arguing can dissuade him from it. Not that he ever changes the default IE search from Bing, mind. I guess he stopped being an up-to-date IT literate around 1998?