The no paper receipt thing bothers me in that how do you prove you haven't shoplifted? I guess they would drag you back in and look on their records?
Also anything you might need a refund for-you are going to need a receipt
If you have it emailed, you will usually have it in your email which you can access from anywhere with internet access whereas a paper receipt can blow away, fall out, get washed, accidentally thrown away, etc...
I know our till saves every purchase made and what time regardless if the receipt was emailed or printed and how it was paid.