I bring my 15PB to work everyday and have always shut it down before i put it in my bag for traveling. This past week I just started closeing the lid (putting it to sleep) and commuting with it like this. I don't see any problems with this but if a techy could give me some info to whether i'm gonna screw something up i would appreciate it. I really don't care about having to shut it down if need be but i prefer to leave it running. Any comments?