[ScottWhigham]

No offense meant but who is "us"? I'd like to look at your site, compare it to my target market, and then decide if I think it's a technique we could use.

The big concern in implementing techniques like this is that the number of (a) abandoned carts rises due to people who have a coupon yet can't figure out how to use it (or didn't read the instructions in your email), and then (b) the number of support requests will rise. If "us" is a company with 1000 customers, I'm not sure that you've tested the scalability of it with promotional emails sent to, say, 50,000 people on a Tuesday morning. Support for shopping cart-related frustrations is one of those "You'd better provide a response ASAP or you will probably lose the sale" types of problems.