The Joneses is an interesting idea: if you push product placements all the way to 11, you'd have it done in real life. But how do you attribute a [growth in] sale of product P, to the "Joneses" team member? Target market of product P + geography of the sale? And what if the network effects is far reaching and has no geographical boundary (i.e. internet)? So, no two "Joneses" teams should pimp the same product? No good.
What if we try something more pre-emptive, using something more direct - FOAF. So when customer Charlie buys Product P, your CRM picks up that amongst other customers who bought P, customer Betty is in Charlie's FOAF network (Facebook, Twitter, email, blog, flickr, etc).
With this knowledge, you could directly credit Betty a referral reward and hope to gain an army of MLM team. But this risks displacing Betty's original reason of buying your product with a weaker, extrinsic motivation.
Alternatively, you could credit Betty with a discount on her next purchase. This approach is good and already exist informally. But it is also unsurprisingly inefficient in its current state: the connection happens if you manage to make the sales assistant remember you and they bother to inquire about referrals when serving a new customer.
Wouldn't it be great if a hypothetical "iCashRegister (now with FOAF)" exist to make this more efficient?
To cap the potential hemorrhage of "discount credits" on heavily connected customers, if there are several customers connected to this new customer, they'd only each get a slice of the credits. Also, for some business, it might make sense to attribute a referral based on the transaction of the same product. For other businesses, it might make sense to attribute a referral based on purchase recency.
So now any customer connected to a subsequent customer gets discount credits. And all this can happen regardless of whether (you) the business owner is servicing the customer, or if it was just your part-time sales assistant in the shop.
To hell with wimpy loyalty cards. Why isn't your business using "iCashRegister (now with FOAF)"?
Update: Do check out Anafore if you're interested in this topic!