1) Automatically send a 10% off coupon to people 5 days after they put an item in their shopping cart but didn't buy it
2) If they convert from that coupon and buy what they initially planned to buy 5 days ago we add them to a list of "win-back buyers"
3) If they convert from that coupon and add additional items we add them to a list of "win-back buyers plus"
4) Wait 3 days and then kick-off a multi-month custom email marketing campaign with various deals, offers and products tailored to what they've bought in the past, their average purchase price, geographic location, sex, age and any of dozens of other metrics we'd have for that user
5) Ask if they want to opt-in to coupons via SMS, send those coupons out the next time they log into the e-commerce website, browsing around before purchase
...and it just goes on from there. This type of long-term marketing/re-marketing, segmentation and advanced campaign management is precisely what email marketers do every day. Most people running email marketing campaigns for ecommerce and brick-and-mortar retailers have been doing customer lifecycle management across various channels (email, direct mail, online advertising, social and more) for awhile and they're very good at it. When you get an email in your inbox from a big retailer you've shopped at before, you may not know why you got the email but there's a good chance you were targeted via specific segmentation and targeting engines across over a dozen datapoints about your past behavior.
And one scary thing most people may not be aware of is that at the very high-end of enterprise email marketing systems, they have "data augmentation" features so that if you only know someone's email address you can pay other companies to give you the rest of their marketing profile, like name, address, age, ethnicity, purchasing behavior (like when you scan VIP cards at supermarkets or use gift cards), and even your full credit profile including credit scores, credit card types, previous addresses, loans you have, what type of car you drive, how big your mortgage is, etc. In fact, CheetahMail, which is the Rolls Royce of email marketing software used by all the largest companies in the world, is actually owned by Experian the company that has all your credit information. http://www.experian.com/cheetahmail/index.html