For a long time the internet/media revolution came at us via the same box - that rectangular one on our desk that we were already doing our spreadsheets on - and it was hard to see all the possibilities it offered because of the box it was in. (It probably didn't help that the box looked quite a bit like a television, so for a lot of the time we ended up thinking of it as one.)
But recently we've started to see the computing and connectivity revolution become embodied in other shapes and forms - things that are smaller, lighter, with different feels and affordances. It's just taking us a while to design to those differences. This feels like the really exciting possibility of the next few years - designing media for new form factors, not new channels.
For example, think about the "Kindleyness" of the Kindle and how it might be used to develop new forms of writing; writing specifically tuned to the Kindle in the same way as the novel is tuned to the printed book.
The Kindle lets you update over the air, for example, so imagine a thriller delivered to you in daily instalments with clues you have to solve in order to unlock the next chapter. Alternatively, since the Kindle lets you highlight sections and share them with people, imagine a story written with that kind of collaborative reading experience in mind.
Consider the fun you could have if you were making comics explicitly for the iPad. Graphics and words that know they fall under the hand like regular comics but could move and make sounds and offer interaction.
I suspect this is where we've gone wrong with all those screens on the Underground and at bus stops. We can only see them as moving posters and not as smart, located displays. Why, for instance, do they only carry one execution at a time?
What if we thought of them like regular screen media - with a bit of useful or interesting content on one half the screen and a commercial message on the other half to get you to look at it? Or what if the two were interposed like programmes and ads on the telly?
For an example of someone who's trying to think this way, have a look at a little experiment from Matthew Irvine Brown. He's written music explicitly designed to exploit the shuffle function in iTunes - you load up dozens of micro-pieces which can be played in any order and still make a coherent piece of music. It's lovely and sounds genuinely new. Check it out at http://bit.ly/f5U762.