An interesting story from NPR this weekend about how we define generations is increasingly based on media, and not on shared experiences.

Prof. ROSEN: Well, one of the interesting things about the teenage generation, the iGeneration...

SIMON: Mm-hmm.

Prof. ROSEN: ...they have learned technology basically from birth. They want to be able to text on mom or dad's phone as soon as they can grab the phone. Whereas the generation just above them, their older brothers and sisters in the Net generation, they certainly came to technology at some point but not as young and not as overwhelmingly prevalent in their lives.

SIMON: And what difference does this make though? Or what differences does it make? Because you lay out a quite a few.

Prof. ROSEN: Well, first of all, the little I in iGeneration stands for both things like the iPod or the iPhone or the Wii, but it also really stands for individualized. And this generation has gotten very used to having things their way. They want all their technology individualized and they want it all available all the time.

And did I not say exactly the same thing over two years ago, when I collaborated with Penelope Trunk on a "What Generation Are You?" test that measured your generational membership in terms of the media you consumed? Yes I did.

Having said that, I think the notion of a generation is often not very useful. I'm technically a Baby Boomer, but at the very end. So why do I have more in common with someone born in, say, 1951 than someone born in 1965?