I would expect the opt-in model to last only until they realize that most people don't bother to read contracts and will sign without reading the small print, and that it's more lucrative for the phone to come with "MyLocal Offers and Opportunities" (i.e. marketing tracking) enabled instead of disabled as a default setting. The more actives they can point to, the more ad dollars they'll get. They want ad dollars.
That, or it helpfully resets to "on" every time you update the phone software, or every time you turn the phone off, then on again, much like "I would like to install toolbar/receive email/etc" checkboxes mysteriously recheck themselves on a software install options screen.