Mostly it's self identification as part of a tribe, in my opinion.
Why do we self-identify in this way? Because we don't just use the technology, we are very deeply involved in creating it, and it gives us a unique perspective on living in a world where technology is ubiquitous.
So, you could pick apart "deeply involved" but you don't have to, because what matters is the unique perspective it creates. That's a thing unto itself, and we call it "geek".
Like any tribe of self-identification, it's much easier to see it from the inside.
I thought the Tech Republic article was pretty awful, or rather it had an awful title, but nobody wants to read about the end of IT. That's really old news. Say "end of geek era" and you get a bunch of clicks from people who currently self-identify as geeks. Say "end of IT" and you get... crickets.
-Jason