This is a very good thought. We send emails to all people who abandon their carts in-checkout and about 50% endup calling us to complete their order. The number on reasons why people were leaving our cart was frustration when one error would cause unrelated data to get dropped. Lyle recently made some great fixes for this. so we will see if conversion rate improves. There is no question that contacting your in-checkout customers is just good customer service.