Probably the most common example these days is spouses who don't email regularly.

Once upon a time, you only got one or two email addresses from your email provider (I'm looking at you, CompuServe and AOL), so at that time it was common for everyone in a family to have a single address. Eventually they added explicit multi-user features -- IIRC, AOL went as high as 5 emails per account before my family moved on.

As in bloggsfamily@localisp.net.au that both parents and all the younger sprogs share. Still common as anything.

One of the things I loved about the original Mad Max film was that they nicknamed their own toddler 'Sprog'...