I carry mine in my pocket "T" shirt all the time, no problem. I've laid mine on it's side, no problem, I've had mine tip over upside down, no problem.
If it's wicked and working right, it doesn't leak. The cotton swells up enough to seal it off very well. I'm very happy with mine, for the most part, and have yet to have it leak on me. I had the same concerns, but after using it for a while, that concern went away.