As a comparison, this is still a greater percentage of people than use Twitter.
From Podcasts: Who still listens to them? on the BBC’s website.
My mother listens to a lot of podcasts and is on Facebook, but she isn’t on Twitter.
Which is also the reason why Twitter is weak where Facebook is not. Despite its popularity among early adopters, it isn’t a mainstream technology, and the people running it don’t seem to have a clue as to how to reach the mainstream.
My mother has heard of both. My father (slightly less computer literate) has heard of both. Even my grandmother has heard of both. You can’t listen to Radio 4, for example, without hearing podcasts mentioned on a regular basis. All regular listeners will know what a podcast is, even if they aren’t interested.
Besides, it’s not a question of what people have heard of, it’s a question of who they perceive the service to be for.
Podcasts are radio episodes on demand. Easy to understand and easy to pitch to those who like radio. The radio stations themselves here in the UK and in Iceland do a lot of the work involved in evangelising podcasts. They mention them in adverts, and they promote them on air with the iPlayer and the like as ways to catch up if you’ve missed an episode.
Twitter, on the other hand, usually doesn’t hook people until they’ve used it, and even then only if they know a lot of other people on the service. The vast majority of people still don’t see the point of Twitter, even after they’ve understood exactly what it does.
The most common response I’ve heard after describing Twitter? “Oh, it’s for geeks, then?”
It doesn’t help that Twitter doesn’t actually add any value to your life, just sucks time away. (There’s a reason why I quit Twitter. I’m not a fan.)
My mother, and most of the mainstream public, know by now exactly what Twitter is. They just aren’t interested.