After the lecture, it's the duty of the lecturer to ensure that all electrical devices are powered down. That means being the last one out of the lecture theatre, sometimes in near pitch dark and aiming for a little square of sunlight in the distance that marks the exit.
I realise I'm no longer afraid of bumping into... metaphysical things in the dark. What I'm more afraid of is bumping into unseen physical objects that could cause unnecessary barking of the shin, or worse. Fortunately today, I made it to the door unscathed.