I think it is what you make of it (or, as you say, it is largely dependent on the kind of person you are, and your actions).

I don't doubt that there are lonely programmers. I think that you'd probably find lonely people for any X that people choose as a major pursuit in their life, though. I think that many (certainly most of the folks I know) programmers are programmers because of the fascination/cool factor/feeling of relative omnipotence/etc that comes along with creating and controlling processes that do cool things (whether for you or for millions of your friends). Within that, there's still a lot of diversity.

Also, you don't need to have a homogenous social circle if you don't want to.