Edit:Sorry, got this wrong. I actually received four stamps that were due, 1 bonus stamp as it was the first time using the app; then, for earning 4 stamps within the first 7 days, they double the stamps - so I got 10 in totoal, which is how I got a complete card, plus one stamp on the next. Asking mods to expire this.
Caffe Nero have launched a new Android and IPhone app which allows you collect the loyalty stamps electronically instead of using paper cards. You can optionally link a payment card to use in store. Once you use the app for your first purchase (can be just to collect stamps) you get one completed card, valid for your next hot drink - expires after 18 months.