When I first moved out to Silicon Valley and started working at Google, I met lots of people that consistently saw things that I missed. Even ones who didn't have as much experience as I did, at least in terms of year-as-a-computer-programmer.
Now that I've been here a couple years, I've found that I'm consistently seeing things that other people are missing. Even, in some cases, the same people that consistently saw things I missed when I joined.
It hasn't been because my innate intelligence has gone up. (In fact, as measured by my performance against the Starcraft: Brood War AI, my reaction time and ability to think quickly seems to be going consistently down since high school.) Rather, I've accumulated lots more domain knowledge. And it's tacit domain knowledge, little subconscious bits that are floating around the Valley culture but that people aren't aware of on a conscious level. If you don't know to look for such domain knowledge, it seems like the person is just massively smarter than you. And if you have that domain knowledge, you usually aren't aware that you have it, and so it seems like you're massively smarter than everyone else. But if you actually look closely at the leaps of logic that intelligent people make, and then trace those solutions back to the knowledge that enables them, you can almost always find some particular fact hidden away in the back of somebody's brain that accounts for it.
It's interesting many traditional software companies seem to promote the idea of "subject matter experts" (SMEs) as a key part of their software development process. Although I think the concept of SMEs is somewhat flawed, the idea that domain knowledge is vitally important becomes more clear to me the longer I spend working in a particular area. You can't be an effective developer in any industry unless you work on building up your domain expertise.