Might have told this story before, but...

A few years back, I went to our local Tesco Extra, and was buttonholed by a polite but persistent oung man who proceded to show me how to use the newly-installed 'Scan and Shop' technology. This involved using my loyalty card to log into the system and activate a handset. I could then trundle round the shop, selecting my items and scanning the barcodes with the handset, before putting them directly into my shopping bag(s). The handset didplayed a list of items I'd scanned, and a running total of expenditure. I wass then to go to a special set of checkouts, where I could transfer the data to the till and pay.

So I stand patiently through all of this, then said to the young chap "You do realise, don't you, that you've just spent twenty minutes teaching a bloke in s StarFleet Academy t-shirt how to use a tricorder?" Lad looks blank, nearby older colleague falls about laughing. Aging nerd one, eager-beaver shop assistant nil!