I have fallen over them before. Quite embarrassing. I run two of them and to suddenly have one cut in front of you in the dark . . . . However, that seemed to help. I also made a concerted effort to keep them farther from me. I haven't had this problem now for almost a year. I am sure I just jinxed myself though!
As for stairs, they gravitated to passing on the left. Since I have several, they tend to barrel down the stairs in a group. The noise warns me, so I can push myself against the wall! I just wish I could harness their daily excitement just to be alive! (I wouldn't mind being able to nap the way they do, either, but that's for another thread!)