That's around the same time that this thread got startedpapercoffee wrote:Uhhhh ...what happened there?

This graph shows the amount of online servers found by the Epic Games masterserver (the zeroes on the bottom of the graph indicate time-outs or moments that the Epic masterserver was inaccessible for unknown reasons). On August 16, something went horribly wrong at Epic, --which, for the record, they still deny-- and essentially all online games went "missing". They may have ran out of memory (we had that at 333networks with the ucc masterserver applet) or they may have had network trouble. In either case, Epic's masterserver stopped registering beacons.
A reboot of the server should have fixed this, but it looks like they choose to ignore the problem away. It looks like memory (or network traffic?) is slowly becoming available again, because in the last half month, the amount of servers is starting to return to the point before the crash.
This is all still speculation, but it definitely looks interesting. Also, the 333networks masterserver has continuously been registering 610~ish UT servers online and was unaffected by whatever happened.