I don't see how a popup that asks for permission in clear and simple terms is dubious at all. I don't want to have to print out the terms and conditions, get them notarized with my signature on them, and snailmail them back to the company when I want to use an app's features in the future, but if explicitly consenting to a popup isn't good enough then I fear that's the path we'd be headed down.
If someone sells me a car, and I paint it pink, and they're mad after the fact because they hate pink, did I fail to adequately convey the consequences of their agreeing to sell me the car? I don't think so; they agreed to sell me the car and that should be enough.