Walls, no walls, here. (bumps into a wall as I write this.)
Okay, so seriously, yes, I do have walls that I've built around me. Part of this is the fear of being rejected, as I have been rejected in the past by peers. (Ah, the joys of childhood.) Usually, these walls are up when I first meet people, or in a situations were I'm very uncomfortable. As I get comfortable, then they start to slowly come down.