Jebus! I've got a couple of these things sitting in my basement! Should I be worried?
Well you may want to take some precautions I would guess. I have a program I wrote monitoring cgminer and the pool to make sure cgminer is running and producing hashes. It will restart cgminer if needed, and also email after a certain amount of time if I'm not mining. So I have a little bit of warning should it burst into flames, but if I'm a couple hours away from home at the time, I can't really do anything about it.
In the past when it would happen I would just assume I lost power at home, now I'm going to worry it's burning down

Yup, the BFL gear is so flaky, I have a combination of scripts & software to automatically restart everything every 2 hours. Even with that, I have to give it all a kick every week or so. In contrast, my BitFury gear is rock solid, I almost forget I have it running.
I'm going to get a Corsair ax760 PSU (as recommended) to replace the BFL PSU's.
It's $200, expensive, I know, but at least I'll be able to sleep.