I had lots of snail-mail penpals until email came along, when some of us switched to emailing and others got lost in the ether. When Facebook became a craze, I lost almost everybody because I refused their exhortations to join (I really don't see the point of "sharing" selfies or pictures of my meals, and REALLY don't see the point of wasting precious time reading non-messages like "LOL" or "You go, gal!" - I mean, what IS that all about?
I imagine a lot of people (me included) would love to have some specific pen-pals we could get to know personally, rather than the faceless interaction of online discussion. But we're all aware now (or should be) of the dangers of letting strangers know exactly who and where we are, before we even know their names.
You never know who you're going to meet online (some people feel this is a great thing, others that it's one of the worst aspects of virtual friendship). To be honest, I've had a few email pals whom I'd really rather not have met! The most notable was an American man whose very first email to me contained a picture of his bent-over behind. Not sure whether he was giving his opinion of me specifically or British folk in general, or maybe the whole of humankind!