If you could care less.
If you could take away from how much you care means that you care.
The author basically says that if you care, but could care less, then it might not be for you.
It's not the author's fault, I hate the phrase because people mix it up.
If you could eat an apple, implies you have an apple to eat.
fixed...
If one doesn't care at all about selfies then the phone is so obviously not for you it doesn't need to be said. If he had said "could not care less" then the rest of the sentence has no point or purpose as it is about marketing to those who do take selfies and care about taking selfies. The selfie phone is not being marketed or designed for those who do not care about selfies or taking them. They are marketing to those that do care about such thing, and the author is questioning if people care enough about them to invest in this phone.