Nicholas Carr hypothesizes that we're seeing a stagnation in transformative innovation because we've shifted towards the top of a sort of Maslow's hierarchy of innovation.

As with Maslow’s hierarchy, you shouldn’t look at my hierarchy as a rigid one. Innovation today continues at all five levels. But the rewards, both monetary and reputational, are greatest at the highest level (Technologies of the Self), which has the effect of shunting investment, attention, and activity in that direction. We’re already physically comfortable, so getting a little more physically comfortable doesn’t seem particularly pressing. We’ve become inward looking, and what we crave are more powerful tools for modifying our internal state or projecting that state outward. An entrepreneur has a greater prospect of fame and riches if he creates, say, a popular social-networking tool than if he creates a faster, more efficient system for mass transit. The arc of innovation, to put a dark spin on it, is toward decadence.
One of the consequences is that, as we move to the top level of the innovation hierarchy, the inventions have less visible, less transformative effects. We’re no longer changing the shape of the physical world or even of society, as it manifests itself in the physical world. We’re altering internal states, transforming the invisible self. Not surprisingly, when you step back and take a broad view, it looks like stagnation – it looks like nothing is changing very much. That’s particularly true when you compare what’s happening today with what happened a hundred years ago, when our focus on Technologies of Prosperity was peaking and our focus on Technologies of Leisure was also rapidly increasing, bringing a highly visible transformation of our physical circumstances.
If the current state of progress disappoints you, don’t blame innovation. Blame yourself.