It should've been neither an opt-out nor an opt-in. Since it's a one-time notification, it should've explained the rationale behind this feature and asked for a decision. That would mean treating users as intelligent adults. Pre-selecting a good-deed option for them is annoying and insulting. I know that I don't like a good Samaritan behavior stuffed down my throat, so I would've gone and disabled this feature just a…
I disagree. This is the cowardly and helpless solution to the problem: When in doubt, throw Yet Another Dialog or installation wizard page in the user's face.
Programs should confidently do Something Sensible by default, and instead let the 25% who want something different be able to easily change it.
Less choices makes more happy: http://en.wikipedia.org/wiki/The_Paradox_of_Choice:_Why_More...