Shopping cart or checkout? I pile stuff in shopping carts and walk away from it all the time, but once I get to the checkout page where the coupon box is displayed, the purchase is going to happen.
Some sites don't give accurate shipping information until final checkout which is really irritating. I'll go through part of the checkout process so I can get a final price and then leave to compare prices.
Even Amazon will let you get pretty far before it tells you that product is not allowed for sale in your region. Worst case was a big ticket ASUS laptop I did plenty of research on (there may be warnings on the product pages IF you are logged in while browsing, I was not).
