People are unlikely to change default settings. So make sure the defaults are optimized for them.
There are good ways and bad ways of doing this. “Click here to NOT receive our weekly spam letter” is a bad way of doing this. It will be effective in the short run, but because people generally don’t like spam, your customers will hate you in the long run.
“Click here to NOT contribute to your retirement plan” is better, because people generally will be happy to have more money for their retirement.
Grocery stores do this with the familiar “Paper or plastic?” The default assumption is you are getting a bag. You have to opt-out of the bag otherwise.
Ash Navabi 