Very odd indeed, to the best of my knowledge the only outage was yesterday from around ~2pm until midnight.
Site tests are performed every 5 minutes and notified after 10 minutes if there's an outage.
I haven't received any emails advising of 'random' outages, yesterday was a fairly rare occurrence.
The only other normal one's would be early hours of the morning for a space of 5 minutes at most when the database backup occurs.