If I want to sign up for a 401(k), a newspaper subscription, a contract for my cell, a subscription to cable, a savings account or would like to receive weekly issues of hairy midget feet illustrated, I will indicate so on some kind of form the respective company is happy to provide. I like my non-neutral starting point. I like to be free to enter in any kind of obligation if and when I choose to; not at the whim of, well, whomever you'd like to decide for you.
Donating organs is, as far as I understand, pretty simple: If you indicate being a donor, your organs are up for grabs* on death. If you indicate not being a donor, they aren't. If you indicate neither, your closest relatives get to decide which one they think you would've wanted. If your and their opinion on the subject differ, they are required by law (at least that's what it's like in Switzerland) to offer your opinion instead of theirs. How well they'll be able to separate those is another question, but as long as you keep the donor card in your wallet, you're good to go.
Enough with the loosely-related topics, let's get back to the browser ballot. Riddle me this: Where does it end? Windows comes with Paint. Why isn't there a Graphics Program Ballot offering Photoshop, Gimp and Paint.NET? Windows comes with a Movie/DVD maker. Where's the Video Editing Ballot offering me Premiere, VirtualDub and avidemux? Windows comes with a Media Player and Media Center. Where's VLC, XBMC, MythTV and so on? Why don't I get a Ballot screen for R and Matlab instead of calc.exe? Why is there no choice between notepad.exe, Notepad++, Notepad2 or SciTe? Why don't I get the choice between WordPad, MS Office, OOo or Star Office?
What I'm trying to say: Forcing such a ballot screen is bullshit. Those who understand what they're doing would probably switch anyways. Those who don't, get confused, click at random and become painfully difficult to support. Stick to one default, cause that way those who did change it will^Ware more likely to realize support for Chrome will have to come from Google, not Microsoft.