Thought:
Have 2 shopping carts upon entering a retail store. One with a small monitor, one without. By 'opting in' to the cart with the monitor, one gets automatic coupons or a flat up-front discount. One must login or create a user account to get the discount. Likely fields would include [sex, name, zipcode, b-day]. Might I suggest further discounts (to gamify the process) for extra fields, for example 3% extra discount for entering if one has children.
Note the implicit wager: the shopper 'bets' that the up front discount will be favorable to the 'up selling ability' of the store. It is therefore incumbent on the store to be as smart as possible. Digital gold, then, is data mining on the wealth of data being created by users (for example on the same store's web property) so that relevant recommendations can be surfaced in a time-dependent fashion resulting in more purchases. Practically speaking this would occur in the context of the isle and the path taken: strolling down the toiletries lane would raise opportunities for recommending, say, that new leg shaving cream, or that new razor that avoids nicks on those square jaw lines. In this example recommending the wrong product not only results in a lost up selling opportunity but also erodes trust in the recommendation system.