We had about 1 hour downtime with a small revert this morning:

All of the equipment in one of our cabinets in Chicago is not responding, suggesting a possible power issue; the machine hosting your server is among those currently offline. We are currently following up with the facility to have someone physically investigate ASAP.

Update @ 10:17am CST: Further investigation determined that this was due to a bad fiber module in the cabinet's switch. We replaced the module with an on-site spare and everything is back online now.