The best programmer (I estimate he is the 10x at least) that I know, has no SO profile, no tumblr, no twitter. Pretty sure, he has not committed any patches to open source projects in recent years. He comes at work, gets more done in 5 hours than a team of 4-5 people, then he leaves to go home to his family. He is the one who can handle 100k project with ease (and probably 1million project). His knowledge of code and the ability to travel move up/down abstraction chain is astounding, he knows more about my source code than me, and he only has glanced on it a few times.
If he was looking for a new job, he would not be able to show the closed source he is working on, as it is a large embedded project.
Granted this is an edge case, but there are programmers like him out there.